Mercedes is saying to resurface rotors for warranty work. You have to question their motives. I assume it's cheaper for Mercedes to have the dealer resurface than to change the rotors. I don't think that's true for a D.I.Y.'er.

I've always bought my rotors from a dealer and have never had a problem. With the old blue anti-rust coating, it used to take more time taking that off than it did changing the rotors. That's no longer a problem.

In any case, I'll bow to the experts.