[quote name='CapAmerica']360, better graphics, better online and I prefer the controller.[/QUOTE]
Wow, way to start a flame war with some mis-information. Technical details aside, graphics will depend entirely on the developer, as both systems are capable of producing high quality visuals.
I no longer have a 360, but if I did, it would depend on a few things. If it's multiplayer, then it depends on community and how many people I know that play the game on either console.
If there's no multiplayer and everything else is equal, I'd go with the PS3 because I prefer trophies over achievements and I prefer the Dual Shock 3 over the 360 controller.
If there are things that affect playability on one console over the other, I'll go with the better one. Bayonetta, for Instance. Sega

ed up the PS3 port, so I'd pick it up on the 360. Darksiders is supposed to have worse screen tearing on the 360, so I'd go with the PS3 version for that.
And lastly, there are just some preferences I have. I'd pick up Final Fantasy XIII on PS3 because it would seem weird to play it on the 360.