360 if you want to pay more for a system that you won't be able to play for weeks because it breaks down so often, has about equal online server quality as the PS3, and will be passed up by the PS3 content-wise.A friend of mine has a 360 and has sent it in twice to be repaired (which has taken about 8 weeks each time).
I have a PS3 and have had it since it's release. Guess what? I haven't had a single error the entire time I've had it, it's free to play online, it has a blu-ray player, the games for it are quickly catching up to the 360, and the updates will soon make the 360 look awful (PS3 Home, check it out).
Sure, the 360 has the Halo series, which weren't bad (but weren't anything special in my opinion) but the PS3 has Resistance: Fall of Man which is 10x better than Halo in my opinion.
Anyway, the 360 is the more-poorly made system with more popular games right now while the PS3 won't break down and (for the moment) has games that aren't as popular.
I would go with the PS3.