Originally Posted by RickN
Brembo drills them mainly for weight savings since BBK rotors are typically big and heavy. I'd stick to drilled too in that case.
Actually Brembo drills them because that's what people want (for asthetics). All their BBK's are available slotted. Brembo actually stated publicly that they spec x-drilled on Porsches, Lambo's, etc because people like the way it looks, not for functional reasons.
All this talk about brakes, and no one has mentioned tires. Tires are what stop the car, brakes just stop the wheels.... Having a $10,000 Brembo brake set is useless for example if you have Kumho 712's. Sure your brakes will never fade, but they'll never be pushed to their limit either.