the initial point of going from steel to alloy is reducing weight. side effect is it looks great. less unsprung weight means less work for ur suspension (sprung is weight of car, unsprung is weight of wheels, springs, shocks, control arms, etc.). u need to look for something that's light, and have good strength for resistance against bending/warping/cracking. most of the time, this is pretty hard to do or hard to get from vendors. as for weight, u can usually obtain this. for the most part, people go for looks instead =).