is more swept area. Same amount of heat being dissipated over a larger area = more cooling. More cooling is advantageous to minimize rotor warping and reduce friction material wear. Good for wear (but is expensive)is carbon fibre for brakes and ceramic for clutches. Both take heat without fade and is very lightweight. Just MO but metal on metal never really seemed like a good idea to me. However, I'll qualify that by saying I've never used Metal Matrixx pads.