1) More difficult
2) Being able to choose your faction.
3) hardcoe mode. --> they can drop the food in my opinion, but what i love about about it is that i'm looking for watersources while exploring. It could use a couple of other tweaks aswell like stimpacks/bottlecaps/... having weight.
Con's
1) Some quest are real junk and feel repetitive/boring. (with the emphasis on "some", there was a good amount fo fun quests aswell. The Fun/Junk ratio seemed better in FO3.).
2) I spend too much time on managing my inventory/items. (Didn't lose so much time on my inventory in FO3)
3) Going overboard with limiting the player: Not being able to max out your stats(*), trying forcing the player to take a certain path (invisible walls & critters)(**), Locking the player out of (too many) quest(**), Perks(***)...
(*)I agree that it was too easy in FO3, something needed to be done... but maxing out stats can add to the fun. Part of the exploration fun in FO3 was collecting all the bobbleheads and skillmagazines. In NV i just don't even bother to look for them because it seems like a waste of time. Maxing out my character was like a personal quest for power(like a fun and beneficial unmarked quest if you will). I never ever used the unarmed skill for example, but i still had fun collecting the magazines and going after the bobblehead. As i stated before, it was too easy in FO3... but IMO they should only have made it (much) harder, not impossible.
(**) I prefer bethesda's open world game approach. FO3 gave the player more freedom on that aspect. And BWAH ... invisible walls? come on!!! Fallout should be everything but a corridor game. "Open world game" loses a part of it's soul here.
FONV does give more freedom by quest-related choices(wich is good). A consequence of your choices (sometimes) results in locking you out of other quest. Logical and realistic in some cases, but if you try to force the player to take the same path over and over, i kinda lose motivation to start over again from scratch just to see the other aspects of the game (and judging by other discussions about "replay value" i'm not the only one).
(***) As for the Perks, I never choose the "fun perks"(like Canibal/Mr sandmand/...) in NV because it seems like a waste They could for example, have made a diffirence between power-perks and fun-perks. The power perks every 2 levels, the fun perks every 5 levels . it's just an example to show that one of their limitations made it less fun... Don't take the example itself too serious
I want to point out that I put the emphasis on "going overboard" when discussing 3). the general concepts of making things harder then FO3 was good and very necessary, they just went a little overboard in my opinion. It really annoyed at times.