It is a material fact that BMW is the "top" car brand in China, way way way ahead of Audi... if you drive an Audi, you're OK, you're rich, but if you drive a BMW, you are at the top.. Not quite sure about MB, but mainland Chinese people are very much obsessed with BMWs. In Hong Kong, things are more equal between the MB, BMW and Audi. There I think is still a very wide preception that MB>BMW>>>Audi.
What you said is really not the truth,even most of the BMW drivers in Chinese car communities think MB's image is higher.
