Drilled have been known to crack. Do not mistake Porsche or Ferrari as drilled. They look drilled but they are actually casted with the dimples in them, big difference.

The main purpose of the slots/dimples are to allow brake dust to escape as the pad is pressed against the disc.

Cooling advantages come from the fin design between the disc. Something street cars don't have and don't need. Nor do they need slots or dimples.