If you want to save some money you can always go with Zimmermann rotors with Akebono brake pads. Don't forget the sensor and if your doing rear brakes you need to deactivate the brake system through the setting while pushing the telephone call button on the steering wheel and then the ok button on the steering wheel and look for something like change brakes or something.
I know Mercedes uses Brembo or Zimmermann for the rotors and for the brake pads it's Jurid and or PAGID. Not sure on our W166 (I have a GLE400). I only use OEM parts since we (shop) has an account with Mercedes.