The car magazine articles of the late 80's used to compare the 300CE (and also later the 24-valve model), the 635CSi and the Jaguar XJS.
The ranking usually ended up:
But, most agreed that the car with the "bank-vault" build quality was the MB. But, the BMW was "more fun" or handled better in the slolam. The Jag was more elegant or pretty.
Stevebfl hits the nail on the head.....a BMW from that era running at autobahn speeds feels wobbly. The MB does not. Even today at 177K miles, my '91 300CE is ROCK SOLID at 80,90,100,110,120....I stopped at 135...but she had some left.
Keep in mind I put good rubber on, keep her well maintained and align the car (as needed) and tires balanced every 5K miles.
Most of my friends drive BMW's. They are fun to drive, but just don't weather as well IMO.