In all side-to-side comparisons I've seen, the Xbox 360's graphics trump the PS3's by a fairly pathetic margin.
I don't get involved in console wars generally because they're even more stupid than OS wars, but from what I understand the PS3 has a bunch complex, impressive sounding hardware that in reality is nearly useless, which is why the Xbox 360, in practice, generally produces better results.
From personal experience, the online experience is better on the 360- almost no one has a PS3, and, after all, the only point to having a console is to play with your friends, as console games are crap.
Also, the Playstation controller is way too small and the joystick positioning is terrible.
Wii may as well be the best option due to the fact that there's more 'party' games that are fun to play with multiple people that are physically together, also due to all of the just-plain-fun Nintendo games available for it.