Here is some good info from a mechanics website:
Contact area
Blank rotors have a larger area in contact with the pads than slotted or drilled rotors. Therefore they provide better braking at the same temperature.
Cooling
To cool the rotor, manufacturers use a vented rotor, not a cross-drilled or slotted rotor.
cross-drilling puts holes perpendicular to the flow of air - they have no cooling effect whilst the wheel is turning.
A cross-drilled or slotted rotor has less thermal mass and thus heats up faster and fades faster.
Dust removal
So far as I know, with modern rotor and pad materials, dust removal is not a significant factor affecting brake performance.
Gas Removal
I can find no scientific evidence that the resin in overheated pads outgasses faster than gas is removed by rotation. (e.g. see
cross-drilled rotors myth)
What is used by people for whom performance is more important than looks?
No aircraft uses slotted or drilled rotors. They need to stop 100 tons of fully loaded aircraft from below V1 speed within the length of the runway.
No Formula One race car uses drilled or slotted rotors.
No NASCAR racer uses drilled or slotted rotors.
So, if gas removal has not been necessary for 50 years, drilled holes and slots do NOT make the brakes run cooler and dust removal does not make the slightest difference in brake performance ... why do you see drilled and slotted rotors on high-end performance cars? Looks.
All that being said, better quality rotors are better than cheap rotors, and new rotors are better than worn rotors. But I agree with forum members who suggest mixing and matching good solid rotors with good pads. They don't all have to come in a package.
If you ever want the ultimate in pads (and the ones we use on police cars) look for pads with the NRS backing plates.