I'd go with the dealer. I have had decent luck with ATE but I have always been told the dealer is the best. From my understanding MB gets the good discs and the aftermarket guys may be selling discs that didn't quite meet MB's spec.

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1969 280SE
2027 Ram 1500
2026 Genesis GV70
2007 Tiara 3200
1988 Egg Harbor 37
1981 Boston Whaler 17