If $$ plays any part in your decision, stay with what you got. A MB rotor is cheaper than a set of pads for a Lexus. Unless you are buying your rotors from a brake chain your rotors are probably one of the best deals going. They list for $$81 and we would charge 69 plus labor to install one. If you want them over the counter they can be found for a lot less.
One real common problem for MB rotor getting a bad rap is brake chains that install life time rock hard pads that wear out rotors quicker than pads and then they double MB suggested list and give you a set of free pads. BTW the pads would cost $39 from someone using MB suggested list price (not all dealers do).