Nothing really, I bought myself a Logitech Driving Force GT wheel/pedal set for GT5
Is the gameplay better with the wheel over the controller?
Fuck yes, it's amazing. It's a completely different game experience with the force feedback, you can feel the wheels losing traction and every bump in the road. The pedals make it a lot easier to hold the right speed in the corners, and the steering wheel naturally turns back with the tires like you're driving a real car. Plus it's a lot of fun when you're drunk.

I tried that shiz in 3-D at the BB down the street from my house. I could feel the warmth from the drivers piss soaking my jeans since I couldnt pull over (silly 24 hour races) it was that amazing