Hi longhorizon,

Base on my observation, I recommend you to get a 2008-2009 E350 4matic. Besides a normal routine maintenance, You will probably have to change the leaky valve cover gasket, transmission plug and rear air spring at some point. The parts are reasonably priced and it's not too hard to do by yourself. Changing the rear air springs can be very time consuming since you have to remove one piece dual exhaust muffler and disconnect the drive shaft before you drop your suspension arms. However, I believe you will find more problems in other models. Here are few things can really go wrong. . .

If you get a MB model with these following features.

SBC; It has a limited product life span and if this thing goes. A Mercedes Benz dealer will not sell you the part so please avoid this model. You won't regret it. This will cost you a fortune and you will hate MB cars for the rest of your life.

Airmatic suspension; A MB E500 has a V8 engine with air suspension all around instead of strut/shock. Just a like strut/shock, you must replace them and you still may run into air leaky situation. If you get a model that I recommend, it has only rear air bags and can be converted to traditional coil spring. :)

Balance shaft sprocket; A MB part supplier made bad parts where the gears can have a premature wear. The replacement procedure is not simple. It involves removing a front engine plate. It's a doable if you have a garage and time. Again, you don't have to worry about it if you choose to go with the model that I recommend.

7 speed transmission conductor plate; Somehow, MB decide not to sell this item, you have to bring your car in if it breaks and you have to let them fix & program it. It will cost you a lot of money. My recommended model with 4matic comes with a 5 speed transmission only. :)

Well, I can tell you more in detail if you are really serious about it. Thanks to all my friends who wants to drive the best or nothing. :-) If you ask me, the W210 (E class) model is wonderful car but I would prefer to get older models like W123, W124 and W125 series. Oh, a MB E320 is actually a great car, just look out for later year that has rust problem.

Which BMW or Audi? Can you narrow it down? :) I have a group of friends who loves their ultimate driving machine. Some Audi engine has a water pump in the back, you have to pull the engine out to replace it. They are really following their slogan, "Never follow."

A very few of 2009-2012 VW TDI engines are having a high pressure fuel pump issues, look out and do a research before you commit. There is a fuel filter on the left side of the engine bay. You can remove the cover to access it, if you see any sign of metal particles, you run.

Good luck.