The only thing that "dimpled" and "slotted" rotors do is decrease rotor mass/cooling area, and introduce stress risers into the rotor where cracks can occur. While this is certainly unlikely on the street, you're not going to get any better performance out of them than a standard "blank."
All the slotting, drilling, zinc-washing, and drilling is for bling only.
Some people will tell you that dimpled and slotted rotors will actually stop better because they "relieve heat faster". I always had a hard time buying into this because heat and friction are what you want. Right? I mean some heat and friction at least. I'd never buy drilled rotors cause they ALWAYS crack, in the end. Might take 'em a while, but it'll happen. If you must have some kind of bling, go dimpled instead of drilled.