I tall depends on what you want. I bought a PS3, mostly because I have had a good experience with sony regarding the ps2, and so far that experience continues. also, if I want to play halo or gears of war, i have about 4 friends who all have a 360, and those games. what would be the point of my getting them to? they are funner played with friends anyway.
the one complaint I have about the PS3 is that there are barely any FPSs that support SPLIT SCREEN multilayer. all of them have online play, but i can't play online because I have satellite, which sucks for gaming. so far, the only games that i know of with split screen support are call of duty, haze, resistance fall of man, borderlands, and army of 2.
the only one I have played is haze, which is fairly limited in the multiplayer department, (although you can play the whole story co-op, but it is split vertically, and I can't figure out how to change it, if you can at all). I plan on getting army of 2 next, because it's cheap and a friend recommended it. (said it was kind of like gears of war)
other than that, as far as I am concerned, it is excellent in every way.
PS: (if you want backwards compatibility, get an older one. newer ones don't have it)