Keep the E class, ditch the ML unless you like big complicated fixes. The inline 6 is a much nicer simpler powertrain, the V6 is not as smooth and much harder to work on and leaks. Fix it up and enjoy a nice profit selling it, then drive the E for free with the profits!

The ML is a do everything vehicle, it is amazing at most things, but lacks any soul or driving emotion. The E class is close, but still has some sort of road feel and connection and is fun to drive hard, the ML is not unless the roads are wet or snow covered, it does not corner well/provide feeling. It does cover long distances well though if your into road trips, and provides excellent highway fuel economy. It does not do so well in the city, you have to try really hard to get some good numbers and keep it real slow. I am sure that is not the case with the E320, much less mass to move.