I think the X5 is pretty well rounded. good luck

 

This.

I don't know what it is about the ML but there is nothing that turns me on about that car.

 

My parents have an 08 ML350 and it is wonderful. The interior is spectacular and I love the way it drives. It's an all around great suv and the 550 having more power and everything should be even better! My pick would be the ML.

 

Impossible to recommend without knowing more about you.

Each SUV you've selected is the big engine variety so you like power and money / depreciation is likely a non-issue as well

I've owned an X5 and driven / considered the ML and Pepper

Pepper = complete overkill in everyway. 5000lb curb weight with a massive engine and offroad capabilities. Tries to be the best of on-road and off-road but doesn't quite get there. Interior is the worst of the bunch

X5 = It's the driver's choice. If you drive all 3 and the x5 doesn't win you over then don't get it.

ML = luxurious and softer than the other two. Merc reliability is hit and miss but this is slightly more balanced for everyday life (x5 has/had runflats)

 

Premium german metal might be your reqt. but if it was me, I'd look at a brand new JGC Overland with the Hemi if you need something now. This may draw a few chuckles from the German fans, but, it looks like a nice rig for the $$. I am waiting for the SRT-8 version to show up myself....rumor 46K base price for approx. 470HP 6.4 L Hemi. We'll see...