Originally Posted by F22Rapture
I would suggest not using tank drive, but rather using a split-thumbstick arcade mode (with one thumbstick being forward movement and a separate one for turning) or one thumbstick for turning and the triggers for throttle. Tank drive is difficult to drive straight in the best of circumstances, but the implicit inaccuracy of the thumbsticks compared to joysticks makes it even more difficult.
Also keep in mind that the Xbox controller has a large deadzone in the middle of the stick that needs to be accounted for, otherwise it won't center properly. The logitech controllers and joysticks don't seem to have that issue so much.
If that works better, that's fine. We used tank drive, so that was the first thought I had. I find that if most of your time is spent using the left stick and buttons, the XBox setup works better, but swapping the left stick and d-pad is more intuitive when both thumbs are on the joysticks. Just personal preference.