PS3, hands down.
As many others pointed out, it doubles up as a Blu-Ray player and well, it's beautiful to look at.
There weren't many games to start with for it but the range is getting better. Hopefully, it'll only improve. But it really depends on the games you like to play. You need to check out what kind of games are already availabe and those that are in the pipe line for each console.
The xbox is good as a media centre extender, the PS3, not so much...but it's still nice to look at.
Though the xbox is so loud, you get annoyed because you can't really use it for too long for media stuff.
I know I haven't helped much, but remember, the PS3 is prettier.
Oh and if you're in the UK, the warranty on the new xbox is no longer 3 years. It's a 1year standard warranty.