Overall the BMW vehicles are among the very best in terms of reliability and quality. The VW Touareg is at the bottom of the heap and even worse than the Jeeps.
The Jeeps are grossly overpriced for what you get or rather what you do not get.
Not a diesel version available in the states but the Toyota 4Runner would be my first pick for a SUV to tow. These are the only SUV's to be built on a truck frame and not a car unibody (as with all the others, including the Jeep). Toyota does make a turbo diesel version that sells in New Zealand and Australia.
The Europeans are at least a generation ahead if not two of the USA car makers when it comes to making diesel engines for passenger cars. Want performance and reliability go with the BMW.