Originally Posted by Chuck33079

Although, one could point out that by definition, a rotor is a heat sink. It, with help from the caliper and pads, converts rotational movement into heat. By removing mass from the rotor in the form of slots or holes, you reduce the total capacity of the heat sink.

Of course, by the time someone makes that argument, we're well past "what works well on my car" and deep into "theoretically better but completely unnoticable to the end user".