Before I begin this anolysis, I'd like to make note of two things:

I am taking into consideration only the experience of playing Fallout 4, not previous Fallout games or any outside canon sources. I am doing this because in contrasting these factions, I am basically asking "What ethical choice should the Sole Survivor make?"

The Minutemen are not going to largely factor into this, since they are unconditionally loyal and do not provoke a war with another faction without the Sole Survivor's decision to as general. Therefore, the Minutemen are not considered a faction for this purpose but rather the Sole Survivor's own followers (despite having a distinct ideology - to organize and assist the people of the Commonwealth, which a player's version of the Sole Survivor may not necessarily sympathize with in all cases). However, their impact will be mentioned at detail.

I've created a metric for this study, a scale of extremism, violence, authoritarianism, and deception. Authoritarianism applies to both the entire Commonwealth and the members of the faction, whereas deception scores higher depending the less transparent the faction is about their agenda to the Sole Survivor and others. Higher scores mean the faction is less ethical, though everything is arguably relative.

The Railroad

A useful starting point would be to address the question - Are the Brotherhood, Railroad, and Institute all unconditionally dedicated to the destruction of the other two? The answer is probably more accurately "almost" than yes, and the Railroad certainly complicates what would otherwise be an all-or-nothing situation. The Railroad is dedicated only to the liberation of synths. There is little indication that they would be concerned if the Brotherhood of Steel came to the Commonwealth only to exterminate super mutants and ghouls, or would oppose the Institute if they abandoned the production and retention of synths in favor of other scientific pursuits. The Railroad embraces rather than fears technology as evidence by their cause as well as the contributions of PAM and Tinker Tom among others.

Dissent is not forbidden by the Railroad, as Deacon states there are differing views on whether only gen. III synths should be saved or all synths - and there is cooperation regardless. The Railroad takes mainly a defensive stance - only striking at the Brotherhood when attacked and the Institute when their secrecy is compromised and an opportunity to free a massive number of synths arises. They accept violence as a necessity but without much apparent enthusiasm for killing people.

One ethically anolyzing the Railroad must first decide whether the cause of liberating synths is right or wrong. Ultimately it rests on how one defines personhood, but Fallout 4 does give every indication that synths are as sentient and self-aware as humans. If the cause to liberate sentient persons from slavery is deemed worthwhile, it then must be decided if it is worth it to destroy potentially valuable Institute technology and kill some to save many. Perhaps the most important question: If the Institute is indeed an oppressor and enslaver, how many people within the Institute are directly guilty of that, and how many deserve to die in order to free more synths? It is worth noting that by the Railroad choosing Z1's plan over Liam's, they may be sacrificing adherence to minimize violence in exchange for an opportunity to gain power and exert influence.

Finally, we must ask how the people of the Commonwealth fare under a victorious Railroad. We can likely conclude the people will have to deal with the consequences of Institute tech destroyed and a few potentially dangerous synths being set loose, otherwise the Railroad does not intend to interfere with anyone's liberty or take the lives of anyone not directly opposed to them.

Extremism Rating: 7

Violence Rating: 6

Authoritarian Rating: 3

Deception Rating: 4

The Institute

Shaun as a leader seems remarkably similar to Desdemona insofar as both seem to express the idea that they do not wish to harm anyone who doesn't harm them first, but are willing to use extreme force to remedy such a situation.

There is much rationalization within the Institute that synths are nothing more than machines and that they as creators are not responsible for the welfare of synths or potential harm caused to them or by them. The Institute is a polar opposite of the Railroad in another fashion: They believe synths should be sacrificed for the benefit of humanity where the Railroad sacrifices humans for the benefit of synths.

Shaun is a manipulative leader. He grants his parent increasing amounts of power in hopes of winning him over and is not swayed by dissent, but always has a calculated, rational counter to any concern of the Sole Survivor. Is Shaun egocentric and selfish? Hard to say. He gives off every indication that the Institute is much bigger than him as a person and that his life is insignificant by comparison, caring only about the future of the Institute on his deathbed rather than preserving his own life. There is a cult of personality around him though. Do the synths of the Institute praise "Father" because they are programmed to or because they want to? This is not known.

He does seem to tolerate dissent among the Directorate though does not extend any mercy to sabotage or treason. It is important to observe that no one in the Institute seems to have a fanatical hatred of any group, or be existentially opposed to anyone who does not interfere. They see synths as property and are very good at rationalizing this idea, but because of this they are blind to things beyond their black and white perspective. The synth at Libertalia, for example, was not always a psychopathic killer from the moment he was freed. His terminal shows he was once a dedicated Minuteman turned brigand by the threat of starvation, who repeatedly tried to do the right thing before giving up on it and accepting his identity as a raider - a very humanlike transformation. Yet Shaun was not wrong in stating that presently, the Commonwealth needed to be protected from this rogue synth.

Extremism Rating: 5

Violence Rating: 6

Authoritarian Rating: 7

Deception Rating: 7

The Brotherhood of Steel

Is the Brotherhood of Steel genocidal? If ghouls, super mutants, and synths are persons, they certainly are. But that is a judgment a person must make. The word genocide can certainly be used unfairly. An extreme animal rights' activist may call meat production genocide and point to the relative intelligence of domesticated animals. The elephant in the room that the Brotherhood of Steel wants to end a whole lot of lives also has to be looked at in the context of the greater good. "War never changes", and all major and important wars have involved mass destruction and deaths of people - which those who wage the war would say is for the sake of protecting humanity as a whole.

The Brotherhood is not particularly merciful toward the people of the Commonwealth though, extorting food from local farmers with no apparent ethical questioning. They are arguably the most dedicated and the most fanatical of any of the three factions. Yet they can see in gray rather than black and white if they squint hard enough. Maxson can be persuaded into sparing Danse, Haylen chose loyalty to her mentor over ideology, and Danse gains some empathy for a synth's right to live by the end.

There is a great respect for loyalty and order within the Brotherhood of Steel. Their troops are dedicated but they do not see them as expendable property as the Institute does their synths. For what its worth, the Brotherhood really never lies. They tell you up front who they are and what they've come to do with some exceptions.

Extremism Rating: 9

Violence Rating: 9

Authoritarian Rating: 7

Deception Rating: 2

I welcome any and all thoughts, criticisms, and commentary!

Brotherhood only goes after ferals, while some members show prejudice against non-ferals not all do as shown by Initiate Clarke and Paladin Danse who likes it when you help out non-feral ghouls. Saying ghouls might be misleading because the BoS leave non-ferals alone so long as they aren't hostile, hence why BoS aren't going guns blazing in Goodneighbor despite Goodneighbor being where a majority of non-feral ghouls live.

The "extorting goods" is one path and that's entirely on the Sole Survivor. Teagan also says that buying the food is also a choice and Teagan is already trying to get clearance from Maxson to have vertibirds follow caravans around as protection which was a tactic that was successful in the capital wasteland and even then they don't ask for supplies for free, they ask for a discount.

See with the caravans being safer said caravans get more money, because they aren't under threat and they can push more goods, the caravans will also have more money because they no longer need to pay off raiders in order to keep from getting attacked and the caravans will be able to hire more people, get more pack brahmin and generally expand trade. That's what happened with Crimson Caravan when the NCR began expanding and threats like raiders became smaller and only on the fringe of society like in New Vegas.

The option to extort, ask for the food as a donation, exterminate the settlers or buy the food is 100% on the Sole Survivor and I guess Teagan for going along with the options otherwise the BoS as a whole aren't responsible for how the goods are acquired, it's like saying the MM or the RR should all be held responsible because one of their members did something bad.

Couple of things.

The Synth, at Libertalia was never a Minuteman. The terminal clearly indicates that a different individual made those entries.

The BOS player is under orders only to arrange for the acquisition of food for the BOS. It is entirely up to the player whether he will extort or pay fair market value.

I would also point out that at no time during FO4 does the BOS actually target NON-feral ghouls. Talking bad about someone is not the same as killing them.

(You know what? Forget I posted anything)

Yeah the group that kidnaps people, replaces them with Synths, then murders them or subjects them to Human experimentation to create super mutants and regards the above ground population as lesser beings then themselves, is less extreme than a group that kills the people and creatures that attack everybody.

The fact that you have totally missed out the main operating procedure of the Institute means that for me your Ethical anolysis is pretty flawed.

The Brotherhood is in an extreme organisation if you consider it extreme to kill Super Mutants (99.9% of whom are hostile cannibals), Raiders, Ferals, Deathclaws etc.......the Brotherhood have no history of persecution of Ghouls.....the genocidal claim about Ghouls is frankly nonsense and simply ignores the lore of the game and the game itself which contains zero moments of Ghouls being killed by the Brotherhood. Ferals are a separate group since you have no choice, all ferals are hostile and are killed on sight by everybody.

Are the Brotherhood genocidal, well no since as was pointed out to me there are no races involved since neither Ghouls or Super Mutants are separate races (or even sub species), they are simply mutated humans. Do they hate the Super Mutants, of course every rational person in the Wasteland hates the the Super Mutants and the Brotherhood has always attempted to eradicate the created menace they represent to everybody else (although SMs will tolerate Ghouls.....perhaps because they don't enjoy the taste).

Synths.......lets be clear the Railroad cares nothing about anything but Gen-3 Synths, human lives do not matter, robots and Gen 1-2 Synths aren't considered people its all about the Gen-3 which look and act human and are being infiltrated into the Commonwealth (and elsewhere) by the Institute and the Railroad. Ethically they are fighting for freedom for Gen-3 Synths but they are willing to put other innocents in harms way to accomplish their mission.

The Brotherhood is extreme because of its murder of synths and Railroad members. Also, the Railroad has internal debates over whether lower synth generations or other robots count.

Rylasasin, frankly I don't understand why this is such a big deal for you.

This quest, one of too few IMO, allows the Player to role play how a faction, the BOS in this case, presents itself to the Commonwealth. I wish all the factions had more quests like this that would allow our characters to influence faction interaction with the Commonwealth as a whole.

The manner in which Proctor Teagan presents you with this quest clearly suggests that his only orders were to secure supplies from local producers. In fact given his tone of voice and body language I suspect he was told to have the BOS rep buy them and he is saying he is ok with an 'any means necessary' approach.

There are few innocents in this kind of world, the farmers themselves try to take you to the cleaners, price wise, and it takes a speech check to get what I consider fair market value. I am awash in caps by this point so I just pay the exorbitant price.

The history of the Minutemen shows that they are capable of being complete scumbags, letting their comrades and innocent civilians be slaughtered over political bickering. It is unfortunate that the Minutemen faction did not get more attention from Bethesda. Since you are rebuilding them, quests like Teagan's would have been perfect for the Minutemen faction.

The Railroad members are themselves extreme in their views since they willingly put Gen-3 Synth lives ahead of human lives....so if we consider it extreme to kill your enemies in a post apocalyptic world then pretty much everybody is extreme.

Internal debates mean nothing in the end, because the Railroad's entire focus is on Gen-3 Synths and they can and will sacrifice humans to save machines.....the argument if Gen-3 are actually 'alive' and deserve rights hasn't for me been won by any side. Those 'murdered' Synths would have been given new memories and then infiltrated into unsuspecting communities, some could become Raiders or lose it and kill some people. The Railroad has as much as the Institute created much of the fear of Synths by its actions.

I've wrote the same myself in earlier topics, its pretty much clear that Teagan doesn't care how you accomplish the mission but I believe its telling that he is looking for a new guy to do the job for him.....in the end the Brotherhood isn't that bothered either way since under Maxson if your not contributing why the hell should the Brotherhood waste resources protecting you. Of course on the West Coast the Brotherhood wouldn't help you either way.

The reality is the wasteland isn't like our western world, there is no judicial system simply the killing of anyone who threatens you.......the EC Brotherhood is by the standards of the day a 'good' organisation.....not a rampaging horde, no wholesale torture and murder, they don't kidnap people, the don't eat their prisoners. Okay the standards for being good are low but while the are 'bigoted' against Gen-3 Synths who are like a red rag to a bull to an organisation dedicated to preventing scientific advances destroying civilisation again they aren't out persecuting the locals because they aren't 'pure' enough or kidnapping, murdering and conducting human experiments on the locals to further their scientific goals.

the synth at the libertalia is not the minuteman. He replaces the minuteman. the minuteman's last name is Wire and i think his first name was edward.

The Brotherhood does not extort people - the player does. Lancer-Captain Kells' mandate is that the Brotherhood protects merchants to earn discounts for trade. So, clearly, the Brotherhood isn't in the extortion racket.

Lets also remember that this thread is about all factions, not just the BOS.

OP, I think you should have included the Minutemen in your assessment, even if Bethesda rather skimped on them. They are the only faction that allows you to completely ignore the MQ, if you wish.

Here's my suggested rating:

Minutemen

Extremism - 3

Violence - 4

Authoritarian - 1

Deception - 1

Murdering synths is only a problem if you think they are people instead of just machines.

Second, how is murdering the RR a bad thing when this happens: If you are already a member of the RR when the Prydwen first arrives, go back to RR HQ. Des holds a briefing where she straight up says she plans to destroy the BOS because they want to kill synths. This happens long before the BOS does anything to the RR. In other words, THE RR WAS PLANNING ON ATTACKING THE BOS FIRST, how is destroying the RR a bad thing considering the RR was straight up planning to kill them all first.

Thank you for this; I had no idea!

Anyone could become a raider or kill people, human or synth. The Railroad probably needs to fine-tune its reprogramming, agreed, but I wouldn't call them blameworthy, per se. And the Railroad doesn't, to my knowledge, endanger innocent human lives (until The Nuclear Option, but everyone except the Institute does that), only their own and those of anti-synth aggressors.

Well, yes, the villains rarely think of themselves as such.

The Brotherhood telegraphed its plans for mass synth slaughter, what do you expect?

The only facepalming stupid thing here is your post.

Yes it's entirely on the SS and Teagan since he goes along with it, it ain't apologetic it's common sense. Also it's pretty easy to lie about how the farmers die when ferals, raiders and super mutants and whoever else are constantly attacking settlements. My anology with the minuteman still stands because guess what, the general and preston wouldn't be able to keep track of everything the Minutemen do. They don't have cameras on each soldier, they don't have constant surveillance so yes, my anology still holds up.

The BoS as a whole are not responsible because they had no way of knowing unless Teagan or the SS come out with it, hell no one has anyway of knowing unless there are survivors which I'm sure a SS cruel enough to do one of four ways wouldn't leave. The BoS do give a crap about people, their entire position in the commonwealth is for three things

1. To fight the Institute
2. To gather tech
3. To protect the people of the commonwealth.

Actually think before saying "oh you're nothing but an apologist" because yes, people lie and yes people cover up things. Again, unless the BoS higher-ups actually know the situation, which they don't, it's all on the SS and Teagan if they get caught, not the BoS. The whole point of taking the extort or kill all settlers options to make the BoS look bad is really damn pathetic.

Like holy crap, do you think leaders are spider-man? Do you think their spider senses go off every time a soldier does something bad? "Oh no one of my soldiers is doing something bad and I know this because ???? General man away!"

News flash, soldiers have gotten away with way worse things and cover ups happen.

No they didn't.

The Railroad is a network of spies, and we've seen agents as far as the Capital Wasteland. It probably didn't take them long to figure out what the Brotherhood came to the Commonwealth for.

But these raiders or killers are only in those communities due to the Railroad and then Bob turns out to be Synth after he's blown away a couple of locals.........this of course lead to hysteria that anybody could be a Synth.

The Railroad endangers humans everytime it uses a Safehouse within a mostly unknowning human community or places reprogrammed Synth into an unknowing community. Since they know the threats both of these acts can bring down on the locals, they should be held responsible to a degree for future human deaths that follow.

That would make sense if Desmona mentioned it.

She does not.

... why does she have to?

Narrative.

People keep saying that morality choices depend upon whether or not you see synths (primarily Gen-3s) as people. I disagree. I believe that Gen-3 synths:

• Are sentient
• Need to be eliminated, as in "no more produced"

Why? Because to me, they are people with mind-control/erasure technology built in. And that is a Technological Abomination that threatens the very definition of human society. The Tute is even arrogant enough to have "Humanity,redefined." as a motto. The level of authoritarianism enabled by this type of technology has been explored many times in science fiction, and it is Never A Good Thing. Hence the production of Gen-3 synths constitutes an existential threat to humanity.

So do I advocate killing all Gen-3s? Actually, I advocate destroying the Tute as the only way to stop them building Gen-3s. Existing Gen-3s, while dangerous, are guiltless regarding their origins and once known, can be worked around. (While they are unknown as such, obviously, nothing can be done.) After all, danger is a part of life in the Falloutverse.

********************************

Aside: as has been noted, internal dissent is not a sign of openess, it is a sign of a strong leader. And strong factions have strong leaders, who are not threatened by strong subordinates with opinions. Only weak cowards surround themselves with yes men.

Well it does depend on whether you see the Gen-3s as people, if you don't any claim that they are being murdered is laughable since you cannot murder an appliance. If they are people than its an different argument as to whether human rights trumps the new synthetic human rights. So your belief leads to different arguments, since there is no way to convince some one who sees them as toasters that they should be given human rights, nor will you convince a pro-Synth supporter that they should just be chucked on a scrap heap or used for spare parts. The argument that they are simply machines is a different one from the argument that they are synthetic and therefore lesser than a human and if a threat to humanity destroyed.

Existing Gen-3 after the death of the Railroad and the Institute would be a mix of reprogrammed locals who could go loco due to the reprogramming and un-reprogrammed Synths who would struggle to survive without help due to little knowledge about the world.

I wouldn't even call wiping out the Railroad murder. whether you want to call them freedom fighters or insurgents, it doesn't matter. The Railroad's efforts to subvert and fight the other organizations in the Commonwealth absolutely disqualifies them from any sort of non-combatant title. No matter how one sided wiping them out felt, they still died a soldier's death.

On top of that, wiping out the Railroad was an important strategic objective. The Brotherhood's objective was to destroy the gen 3 synths which necessitated the destruction of the Institute where they were manufactured and where they would be mostly concentrated. The Institute had a hole, though, through which synths leaked out into the wild. Obviously that hole was the Railroad. If the Brotherhood had ignored the Railroad, the moment they started kicking down the Institute's door, there would have been a flood of synths trying to escape out that hole. The Brotherhood's job exponentially more difficult. So the Brotherhood did the logical thing. They plugged the hole first. That way, when synths tried to flee, they had no where to go, making it much easier to catch them.

So no, wiping out the Railroad wasn't murder. It was eliminating an enemy that would hinder the mission. It was war.

This is a great post. Thanks for sharing your thoughts.

I've spent a lot of time debating the ethics of the various factions in Fallout 4. I think one of the key points that all of this is really hinged on is simply: Are synths to be considered sentient in the same sense as a human?

As far as AI in general is concerned, I tend to be in the camp of Searle's 'Chinese Room' thought experiment. To sum it up for those who aren't familiar - Suppose you take a person who doesn't speak Chinese and put them in a room. This room is lined with books containing Chinese writing. There is a set of rules, in English, explaining how to correlate given symbols to other given symbols. Through one slot in the wall, questions in Chinese are fed into the room. Using the English instructions, the person is able to correlate the symbols and copy down the answers. This person doesn't understand what the question means, or what the answer means since they cannot read Chinese. They're simply using a set of instructions to correlate a Chinese answer to a Chinese question. The answers then get fed out through another slot in the wall.

Someone who reads the answer is convinced that 'the room/person' can in fact read and write in Chinese. They are interpreting the questions, and giving the appropriate answers. However, we know that this person doesn't actually speak Chinese. They're simply using a set of instructions to match an input to an appropriate output. This is a very over simplified explanation of the scenario, and if anyone's interested there is a TON of discussion about it online (just Google 'Chinese Room experiment). This is one of my favorite arguments relating to AI in general.

Compare this to a synth. To an outside observer they look like a person and seem to interact like a person. However, they are still a creation. They are a product of a very complex array of technology. They perfectly imitate life...but is it correct to actually consider them to BE life? Synths are essentially running on an enormously complex computer program. They malfunction. They can have faulty programming. The 'free will' that some synths exhibit is even regarded by most of the Institute as nothing more than a programming error. Essentially, someone made a typo in a line of code somewhere. Is this the case or are they actually so enormously complex that they legitimately have developed genuine free will? I don't really have an answer to this. However, I tend toward the view that synths can't legitimately be considered as life. Incredibly lifelike, yes. But this isn't the same as being life.

The Railroad comes across as the most moral of the factions (I too am basically excluding the Minutemen from this discussion), but I'm not so sure that this is really the case. They believe that synths truly are life and that they deserve to be liberated. However, what is one of the things that they often do to help protect liberated synths? They change their programming to give them a new identity. They systematically remove their memories and all knowledge of their former identity. Doing this with a synth is apparently a pretty straightforward process because they have actual programming to change in the first place. There are of course various functionalist views of supervenience in the mind-body problem within philosophical argument, which is essentially the argument that the brain itself is nothing but an enormously complex biological computer and that your thoughts and actions are nothing more then executable lines of code running on this computer. That's relevant to this discussion, but for the sake of simplicity (and not writing a novel in this thread), I'm assuming that these types of views aren't playing into the discussion. Simply put, I feel like the views of the Railroad are noble, but incredibly misguided.

The obvious, and intentional comparison that is made with the Railroad is the actual Underground Railroad. The goals and methods of the Railroad are typically seen within the context of the real life Underground Railroad, and they are typically regarded in much the same way. I don't see this is being an entirely valid direct comparison to make. Disregarding the racist views of the days of the Underground Railroad (and even the racist views of today), it is absolutely unquestionable that black people are people in every possible sense of the word. There is absolutely no rational argument against this fact. The ethics of the Underground Railroad can't reasonably be questioned because of this. In contrast, it is most certainly valid to ask the question: "Are synths human?" Regardless of the answer, there is a valid argument to be made on both sides of the debate. I'm not going to delve into this argument any further than I already have, but the fact that there even is a legitimate debate about this in the first place is quite telling in my opinion. This debate hits even more of a gray area when one considers the fact that there is a great deal of internal debate over whether or not Gen II or even Gen I synths should be considered life. I think it's fairly clear that Gen II, and especially Gen I synths are significantly less lifelike than the Gen III synths. This raises a lot of questions about the ethics of the Railroad. I don't see them as really doing much for "the general good" of the Commonwealth. That's not really their goal. They have a very singular purpose...to liberate the synths that they see as enslaved people. Beyond this, their goals aren't really going to affect the Commonwealth as a whole.

Regarding the Institute...I don't feel that there's much to say about them. They claim to be doing their work for the good of the Commonwealth, but they never convinced me that this was entirely true. They are a very self-serving faction. They may operate under the guise of "the greater good," but (not trying to enact Godwin's Law here) so were the Nazis. They dreamed of a superior, perfect human. This is precisely what the Institute dreams of. They claim that they're working for the good of the Commonwealth, but they really don't even know much about the Commonwealth. Abducting people and presumably killing them, then replacing them with synths just to perform their own experiments is completely ethically bankrupt. Abducting children from their parents (as Shaun was) to obtain a perfect specimen for their experiments is completely ethically bankrupt. All of the key members of the Institute convey a very prejudicial view of the 'surface dwellers' and see them as lesser than themselves. They're virtually unaware of the fact that people have rebuilt thriving communities full of happy and prosperous people, despite the fact that they themselves have abducted people and inserted synths into roles in these communities. They're aware of it, but they don't really acknowledge it. One can argue that the Sole Survivor can change a lot of this once they take over as the director, but I'm not sure that this is entirely relevant to the discussion. If we're talking solely about their ethics as they're presented to us, the Institute doesn't have much going for them.

The Brotherhood comes across as incredibly authoritarian and prejudicial, and in many respects they are. However, the Brotherhood never sends us out to clear out non-feral ghouls. They never send us out to kill people (aside from Raiders and Gunners, who do actually present a threat to the Commonwealth), and the things that they do are, for the most part, actually for the betterment of the Commonwealth. They have some questionable practices, such as strong-arming farmers into handing over their crops. The option to simply buy the crops from the farmers is there, and it is the path that I personally chose, however the Brotherhood isn't really presenting this as the 'intended' method. When I bought the crops, I paid out of pocket. I wasn't given a budget, and I wasn't reimbursed for my expenses. Generally speaking, the intended path is to use threats or violence to acquire them. The Brotherhood wants to take out the Institute, which I see as a mostly good move for all of the reasons I've listed previously. The main thing worth questioning here is the fact that the Brotherhood wants to take out the Railroad. As far as I can tell, there really is no good reason for this. The Railroad isn't presenting a threat to the Brotherhood. Yes, if you take the Railroad path you do end up destroying the Prydwen, but this is only because the Railroad was attacked by the Brotherhood in the first place. They see the Railroad as something of a threat because of the fact that they sympathize with synths. However, by destroying the Institute, they are cutting off the only source of synths. Of course there will still be a handful of freed synths out in the Commonwealth thanks to the work of the Railroad...but once the Institute is destroyed, the existence of the Railroad basically becomes unnecessary. There are no more synths to free. Once the already freed synths are tended to, the Railroad becomes basically nothing more than a group of people hanging out and reminiscing about the old days.

On the whole though, I feel like the Brotherhood is the faction that's actually doing the most to actually better the Commonwealth. They do mercilessly attack feral ghouls and super mutants, but I don't think the ethics of this can be questioned too terribly much. Feral ghouls are nothing but a threat and an infestation. Super mutants are incredibly hostile to people. They see themselves as the superior race of the Commonwealth, and they regularly attack people without provocation in an attempt to cement this superiority. They do pose a real threat to people. I think there are arguments to be made either way, but generally speaking I feel like the elimination of feral ghouls and super mutants is nothing but a good thing for the people of the Commonwealth.

Just to briefly touch on the Minutemen, I don't think their ethics can be questioned too terribly much. They don't possess a real 'desire' to wipe out the other factions. They only attack once they themselves have already been attacked. Their only real goal is to protect the people...not necessarily to go to war against everything that presents a potential threat to people. They are (the vast majority of the time) a defensive force. The Brotherhood takes a very offensive approach to the problems. They actively seek the threats out and eliminate them. The Minutemen only go after the things that have directly attacked people. This is a huge distinction. Realistically, I think the best future for the Commonwealth hinges on some combination of the Brotherhood of Steel and the Minutemen. In a general sense, the Brotherhood takes the battle to the front lines while the Minutemen protect the rear and the flanks. Obviously this isn't how the game necessarily plays out depending on how you finish it, but these endings are based more on the decisions of the Sole Survivor than they are on the ethics of the factions themselves.

I said I was trying not to write a novel, and it looks like I basically have anyway. This is a very thought provoking topic though, and it's one that I'm going to continue mulling over for quite some time.