Instead of hand-feeding you info, I would recommend checking them out and doing some research. Here are a few links for you though:
http://www.mbusa.com/brand/container.jsp?/models/class_overview.jsp&modelCode=ml_class_main
http://pw1.netcom.com/~klazys/CARPAGE2.html
http://www.edmunds.com/reviews/comparison/articles/43903/page010.html
http://www.intellichoice.com/reports/vehicleReport.cfm/section/reviews/vhcl_nmb/9361
Use your web browser and feel free to look at the posts here in the ML forum.
Go to the dealer, pick up some literature, and they'll probably be more than happy to go out on a road test with you.
Buy the newest one you can afford. Try both a V6 and V8 version, the power difference is significant.
Gilly