The Mercedes-recommended coolant is made for them by Ashland. It is a low phosphate, hybrid organic acid technology (HOAT), long life coolant/antifreeze. In engineering terms, everything I have read discusses the need for a stable chemistry that will not react with the materials that it comes in contact with. The Zerex G-05 is the same as M-B Coolant.
Read more and make up your own mind.
http://www.valvoline.com/zerex/automaker.asp