In short, a big warning about the MB self-leveling suspension: Can of Worms!!
It is about old enough to start having major reliability issues with it, and once one of the components go, shocks, pumps controller, which seem to go all at once,you will find yourself cursing at it. If anything look at '95 and later MB wagons.
The 940 if well maintanined is probably the better choice, even if it has over 200k miles. The 850 wagon is low miles, and would interest me only because it's a wagon, probably has many more good miles left before major work is needed. The 5 cyl fwd may not be my choice, but it is a good reliable engine, better mileage than the 940 and more powerful.