Wow, hard to believe no one has mentioned one of the key things for me....the XBox controller is better then the PS3. The left thumb position should be an analog stick, not the d pad. I even had a PS1 and PS2, and the XBox layout is far superior.
Outside of that the PS3 is better, but if I had to play the exact same game on an Xbox360 or PS3, I would always play on the Xbox360 simply for the controller. Although if I didn't have a system today and wanted to buy one it would be the PS3, yet the controller is the one this that really helps the Xbox IMO.
and hey, the controller works on my computer too. I don't use it often, but for Batman Arkham Asylum it worked great. A controller is great for a beat em up/stealth game. The graphics are better on PC, plus is adds physics not on consoles. Probably a minor plus for some, but a nice plus for me.