Holes dissapate heat. Try taking temp reading with an infrared thermometer next time. My cross drilled rotor ran cooler on average than my solid rotors. My solid rotors also warped faster than the slotted/cross drilled.
This can be argued about as much as the muffler/hp debate. Btw the holes aren't just for looks, and if your "road race" buddies think its just a way to sell a product, well they should probably just park their cars and try a different hobby.
The holes are designed to dissapate heat, gas as well as water from the surface of the rotor. On road and off, it has been proven to work as they also reduce brake fade.
My rotor set was r1 concepts.