As for will it make you faster or slower....
If you've been playing console racing games with a controller and don't drive or haven't driven in real life much, then it may make you slower at first.
On the other hand, if you've been driving for 20 years for real and don't play console games, then I don't see how it would be slower. A wheel is how you drive a real car.
I've been racing in computer games for 15 years and have always had a wheel, so I don't have experience with a game pad. But I still don't see how it could be slower switching to a wheel unless you have never driven a real car.