I am looking for a set of 15x8 wheels with a 5x5.5 bolt pattern. But I cannot decide if I should go aluminum or steel. The steel should be stronger, but the aluminum (cast) should be lighter. And for new wheels the aluminum is twice the price of new steel wheels. However, I can find a used set of wheels (I think they are modular or something like that) and I don't know if I should just buy new wheels or just buy a used set? And how much of a weight difference is there?