I am not quite sure if you can say that a wheel and pedal user is automatically faster than a driver with another input device.
Personally I am driving with keyboard because that works best for me. I tried controller and wheel too at arcade mode. But due to my lack of driving ability I cannot drive faster with controller or wheel.
But besides the fact that wheel users like Kain, FastAgain or Stingray are way faster than me and not beatable there are some pad users that are in the same way faster and unbeatable like Headhunter and BlackHorse.
So maybe the fastest drivers could write down here who is fastest when they are racing each other and we can see if there is really an input device that brings more performance than the other or if it depends on the drivers ability.
My limit is definitely not the input device. Its my poor performance.