Somewhere in the center differential of a 4matic is a seal. This seal maintains a barrier between the differential and transmission, and is ALWAYS under some 3,000 psi of pressure. Hence, this seal leaks consistently and requires a rebuilt diff go in. On a 4matic there's apparently no way to avoid this recurring problem.
Stick with the 2wd, and buy snow tires if you need them. I've never gotten stuck here in New England with this formula!
"If everything seems under control, you're simply not going fast enough" --Mario Andretti
1995 E500 street car
1986 Porsche 944 Turbo S track car