To be honest after playing multiple racing games with a 360 controller the PS3 one really kind of sucks for racing games. For one the buttons are pressure sensitive, so you really have to keep on pushing to be sure u are going flat out. I remember the same problem with the PS2 games of Gran Turismo and ending up using an old PS1 dual shock controller without pressure sensitive buttons. Besides that, using the analog stick for acceleration is really uncomfortable after 2 or more laps, and the R buttons are to slippery to use aswell.
The X360's shoulder buttons really resemble a gas/brake pedal way better, and offer way more accuracy for dosing your gas. Really wish PS3 hade a controller like that for racing.







