unless you race you wont need them.
Frozen rotors are good because they cryo temper the metal by freezing it. Doing it this way brings it to a nice rockwell rating that isn't too brittle nor is it too soft. But if they temper it like normal rotors then it will actually be made slighly more likely to warp.
This can how ever be very good for cross drilled rotors because the rockwell rating will be low enough to not warp under most conditions but will be soft enough to prevent cracking.
The reason why rotors crack is that there tempered too much usually with cross drilled because the theory is that the harder it is the better it is. but actually with cross drilled the rockwell rating should be lower because the cooling factor of the cross drilled is fast enough to prevent warping but not enough to prevent cracking.
Slotted rotor are usually tempered lower because its assumed that it will have enough integrety to with stand higher temperature; unfortunatly this is why there prone to warping. The end result you can either buy solid rotors or really expensive rotors with designers that take this into effect rather than just coppying everyone else. Just a metalugical rant