People say drilled are weaker and will crack. Slotted has less material removed and stops glazing. Blanks have more surface area but will heat up and possibly glaze.

If I had to personally pick, I would go slotted.

Blank on the cobra setup on my 93

 

You are right about the cross drilled developing cracks but that usually happens if the holes aren't chamfered.....the non chamfered rotors are much cheaper so buyer beware.