PC. PC, PC, PC. Modding is the reason why. And I still like my shooter gameplay with keyboard and mouse, thank you very much. ^_^
I would say PS3 all the way, but in all honesty I would just get bored doing the same thing over and over. I really wanna play it on PC because of the addition of mods, adding countless amount of hours of replay value, but, I don't feel like funding a computer for the game.
It would not be too hard to get a PC that runs Fallout 3 in greatest detail at a decent resolution for about 600 bucks. So I would say that also will apply to NV. You're buying for the future, after all. ^_^