jr. mechanic pretty much nailed it on the head, and 350rs did bring up a good point-less weight. less unsprung weight and less rotating mass. may change by a hundredth on a 10 second car, but that counts. also, most drag racing brakes ive seen are a solid, non vented style.
the zinc coating is on there to keep rust from growing on non friction surfaces. and one down side is drilled/slotted rotors cant be properly lathed, and are also prone to cracking

 

most drag brakes are about a half inch thick thats y they dont have vents wierd how they dont warp at the track. wish they were ok for the street id be all over the strange brakes

 

heh guess i should of been quiet eh? sorry for bringing that up . but they do look nice .