Both House and the NCR are perfectly capable of pacifying the Mojave so in the end it's a choice between what kind of society you want to see and it makes absolutely no sense to pick the Legion unless you support the horrible things they openly practice.
I believe that the NCR will fall in a couple of decades and that once they do then all their land that they control will be split up and once again we're back to Fallout 1/2 where everyone is independent which will only raise the number of gangs, cults, raiders and corruption.
And House thinks about his city and the Mojave, not entire states.
Legion on the other hand I don't believe will fall in at least a century at minimum, and that's if the NCR goes on an obsessed killing spree on them.
So that's why I support Legion.
NCR is falling apart day by day and will soon enough crumble under their own incompetence, greed and inefficiency.
Once that happens then everything they will have worked for will be back to square one.
Humanity needs to move forward and not stagnate in the same anarchistic state that it's been in.
Legion is the only one capable of this, it won't be a pleasant society but it will be a necessity for the world to rebuild.
Every country has it's dark history, Legion is the dark history of this new world, a history needed to bring order to the wasteland.
Doesn't mean that I like what Legion does, I don't.
But if that's what necessary for the world to finally come together under one banner and prosper then so be it.
So would I rather that everything else is in chaos while one city remains prosperous?
Would I rather that the west coast has a decade or five of "okay" order and then have it crumble?
Or would I rather have a nation that can truly stabilize the wasteland for centuries to come and in time evolve to a more free society that's more accepting of personal beliefs?
Note: This does not mean that it's a "fact" that NCR will crumble, it's entirely
my perspective of NCR. But it's for this reason that I support Legion. If NCR were more stable and could actually control their damn lands then I'd be on their side. Yet, they can't. So Legion is the only logical choice for
me.