joycie,
Most knowledgable people will tell you that "Drilled" rotors provide superior performance, however they are not recommended for street use. The intense heating and cooling over extended periods of highway use will usually cause cracks at the stress points created by the drilled holes.
In racing applications, the rotors are changed every few races or every few thousand miles which is not really practical for a street driven vehicle. Also, most rotors used in racing will be made of stainless steel or some other exotic and expensive metal alloy. Rotors for street vehicles are basicly cast iron and much more prone to cracking, etc.
Slotted rotors are fine for street use and still provide better cooling and performance with far less risk of cracking.
...Rich