We seriously considered the ML 320 BlueTec when we got out 2009 35d. What made the choice easier was an extended test drive of both on twisty, hilly 2 lane country roads at night. I strongly recommend you do this prior to making any decision. Preferably do the test drives in the rain.

Be sure to drive the ML long enough to judge the comfort of the seats on a long trip and get familiar with the various stalks on the steering column, especially the shifter and cruise control. And really pay attention to the differences between the iDrive controller and multi-button M-B Command system.

FWIW the choice for us was not a slam dunk. But in the end, we felt the X5 was better overall largely because we never got comfortable with the M-B driver controls and handling.

Funf Dreisig