Small differences, but not surprising to me. First of all, I bet many of us are used to the GameCube controller, and it seems you can make turns a little quicker that way (slam stick in one direction and the effect's instantaneous). Wheel's more realistic but there might be slight lag moving it completely in one direction. Wii Remote I never expected to work well, since pointing a wand doesn't make sense for steering (I've never played Mario Kart Wii, but I assume that's how the remote works in that game).
As for the nunchuk getting the best time for bike... well, the times are very similar to that of the GameCube controller, which makes sense since the nunchuk too has a control stick on it.
So again, no surprise.