I would also caution against fitting drilled or slotted rotors to anything that ventures off road. You are asking for something to get lodged in there and wreak havoc. The new Porsche Cayenne has neither slotted nor drilled but huge flat faced rotors, while most other models in the line-up wear drilled versions.

__________________
1995 G320
1984 280GE
1971 Unimog 416