[bnj]

You want to have as light wheels as your budget allows. When it comes to handling it is very clear, light rims are better hands down.

Traction then. I would think that after a bump where the wheel is getting a hit upwards, more mass of the heavier wheel is harder for the suspension to push back to the ground to gain traction again. I would assume that the force downward (needed to create traction) has less variance during a road course with light wheels. Any difference in the traction must be pretty marginal. All in all, the rims are chosen to be light especially because of the handling (not traction), the tires are chosen to be sticky for the traction.