The slots in the rotors allow gases to escape. 2 piece rotors are lighter and don't transfer as much heat to the hub/bearing as well as reduce/prevent warping , can also just replace the rotor, and reuse the hat, some 2 piece rotors are floating which allow the brakes to fully release and the pads not drag - running cooler. The "venting" in the middle plays a huge part - different mfg's use different vein designs, some have better flow and more surface area which result in better/faster cooling.
Pads make a huge difference - rotors will help with fade as the "upgraded" ones will cool faster. Performance pads have higher operating temps and will reduce fade as well.
I recommend the StopTech, I've drank their cool aid and it is good. Also made in the USA.