I just read the internal MB sales flash on the X5. Their point of comparison is to the ML and having driven the GL and ML I would agree. The GL is a much bigger vehicle. I foud the Diesel to be best - very linear power, and like the best of MB turbo diesels there is virtually no lag. That said - I do not believe in off roading in a $50k plus vehicle with metallic paint (unless the metalic is rust).

The X5 is more of a sports vehicle. In reading the sales material, it is clear that MB sees it as a "formidable product".

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07 X5 E70 4.8i
04 Z4 E85 3.0