I have driven blank, slotted, and drilled rotors on the track and I could notice a difference. I prefer the drilled rotors without a doubt. Does it really help me shave time off? Unknown; but I definitely like the feel of the drilled rotors. YMMV.
Drilled rotors will definitely crack out over time and the harder you use the brakes, the sooner this will happen. I replace my rotors with every pad change so the cracking isn't an issue for me but it is slightly more costly to do it this way (but worth it to me).
http://986forum.com/forums/general-discussions/43520-i-think-its-time-change-rotors.html
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