Both drilled or slotted will assist with dispersing gasses, water and dust. Drilled rotors
have been known to crack over time, around the holes. Slotted rotors work just as well, but will cause an increase in pad wear. Look neat though. Stay away from drilled & slotted rotors, just "bling" for street machines IMO..I do hope we are talking about the standard SL-C Brembo units.