and hands up those of us that do/have raced that have seen drilled discs crack and/or otherwise fail and luckily lived to tell the tale.......
Vented

Slotting

Drilled
as has been said, venting is very usefull to reduce fade.
If you don't hammer your brakes (I do) they may be a waste of money, although I view it as a safety issue, so would fit them, regardless if you thought they are overkill or not as you never know when you may have to tow something heavy down a mountain side.
Slotting increases initial pad bite by venting the gasses that build up between the pad and disc face and helps to keep the pads de-glazed and reduces or eliminates taper wear of the pad.
Drilling can be more effective in these endevours than slotting, at the expense of disc and pad life. Unfortunately the holes create extremely effective stress raisers that propogate thermal cracks at an alarming rate.
Yes, Porsche uses them on some models (I believe these are cast, not drilled) and some (not many) race cars use them, but they are 'lifed', ie. chucked before they start to crack too badly.
I used to keep a massively cracked race disc hanging above my desk as a reminder of my stupidity ........
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