kelsey hayes vs f/m/j swap

I would ask the question as to why do MOST High End Performance Cars , Motorcycles and Aftermarket H.P. Calipers are 4 to 6 Piston Calipers ? Super trooper 455 I would stay with and MY car has K/H Brakes. The only draw back I see and am dealing with now is Wheel selection. Hope my input helps.....:D