If rotors are difficult to Cad plate, I'm curious as to why so many companies offer it on their rotors. Another way to add $$$?

I've located a couple of places locally that will plate rotors for me. Just not sure what all the pluses and minuses are. I had someone recently tell me Cad plating causes pulsating during braking due to uneven surfaces. Is that a legitimate concern as well?

Oh and whats grit blasting?

__________________
'99 CLK430 Blk Coupe