much better handling, unsprung weight just sits on the road with no control of how it reacts, bits that are always the same height and weight without weight shifting for better handling cause big problems.
you can't alter the car to accomodate how wheels work really, but you can tighten the shocks and stiffen the springs to make the shell move less, there is no give in unsprung weight.

probably not the best eplaination, but it's all positive.
the ideal is to have everything suspended on springs but this can't happen as contact is needed to the road on a rotating wheel.