Interesting question. I hope i can give you some hard bought experience.
I drive a 1999 BMW 528 (56k miles ) and my wife drives a 1998 E430 ( 80 k miles) we bought both new and has serviced both at the dealer at all reccommended intervals.
Besides oil changes I have replaced the front brakes and the Mass Airflow sensor on the BMW.
On the MB I have replaced every outside light bulb on the car. the Air Cond compressor, the Harmonic Balancer, Sunroof motor. all four power window motors. the battery, 2 valve cover gaskets front and rear brake pads and rotors, both outside mirrors. And very high priced rotuine service prices.
I like both cars yes somehow my wife got the v8 but I must admit that I have been shocked on the problems with the MB.