Ps3- higher quality console, has a 3% failure rate vs xbox near 20%. Ps3 is also great for home media entertainment, bluray etc etc
xbox 360- hair better graphically because developers are too lazy to use the ps3's full potential (But when a game is using the ps3's full power they look pretty amazing, refer to god of war 3 and other exclusive ps3 titles). 60 dollars a year for xbox live, but it is claimed to have a better service. (Personally from using ps3's multiplayer, I found it to work just fine without lag, but up to you). Xbox is known to have a few more titles, again up to you if that's what you prefer.
IMO ps3 is a better buy. I still have a original ps2 that hasn't failed yet, I wouldn't put my money in a console that needs to be replaced every few months to year or 2.