Slotted rotors are indeed harder on pads. From talking with a number of companies selling rotors, I have heard over and over that for fade resistance, the slotted was the way to do. But I went cross drilled as I didn't want to go through pads so quickly.
Really, the best way of improving braking is to go with a larger rotor, but yes it is more expensive and my personal preference. Quality of rotor material plays a role in warpage and breaking performance for a given size. I feel the Stillen rotor was better in that respect, but the cross drilling and some loss of surface area may negate some of that advantage?
My brother who is a machinist by trade, and a plant engineer for a large casting company, demonstrated that to me. He did machine some of some of his own rotors for his bike using meehanite. The braking performance of this cast iron was excellent, down right scary on his bike. He never did pursue a set for his car however as it was a pretty expensive endeavor.
http://www.meehanite.com/
I don't understand the automotive industry in some respects as to why it is so difficult to get a stock vehicle already equipped with a high quality braking system. In the past, it would stand to reason that some goofball with high performance brakes could apply medium pressure on the pedal and potentially lock up the brakes, skidding out of control. That might be a liability for manufacturers. But with the advent of ABS in today's cars, it would seem that wouldn't be a problem.
My guess is that outside of cost, it would be a liability to have vehicles on the road with 60-0 braking distances of 100 feet, where the rest of the cars on the road are in that 160-200 feet arena, so mediocrity is the result.