It still boils down to what an individual buyer likes. I strongly suspect that MB drivers simply prefer the look, feel, and driving enjoyment that MB delivers.

It's the little subconscious things like whether the body lines and paint scheme appeal to me. For instance, my '92 Sportline simply looks better to my eye than a standard 300E. The lower stance changes the appearance.
I had a customer that had a white '94 S500. I thought it looked ugly. I now have a Black Opal '97 S320, which looks very much more appealing to my eye.

I test drove a Toyota Forerunner a few years ago. Closing the driver's door echoed the flimsy nature of the door construction. I have a Toyota Tacoma 2 WD truck. Totally bulletproof. It does it's job, but you wouldn't want to take it on a long trip. Test drove a Honda Pilot last year. It wandered slightly on the highway. Cross it off. Salesman didn't know what to say.

However, the vast majority of the car buying public has no concept of little nuisances in handling or other issues. Most of them have never experienced what a really well designed car delivers. So they have no basis for comparison and they don't care anyway.

Steve