depends on your gameplay style
I'm a 360 gamer as i very rarely play SP games.
I just get bored playing by myself (no pun intended :P)
and I love co-op gameplay so the 360's better for me as it seems to have more multiplayer/co-op based games. (although now i suppose MOST major games are released on both consoles).
whereas i've found playstation better for the rpg/single player gamer.