[bobcowan]

Drilled holes and dimples are simply for bling. They provide no additional performance advantage. The holes have a tendency to propagate stress cracks, which require rotor replacement.

Slots are there to shave off a small amount of material with each sweep - kind of like a cheese slicer. When you're racing, the pads can get glazed from repeated hard stops. The slots help to keep a fresh surface.

On the street, or with autocross and drag racing, simple solid rotors are the most effective with a low cost.