Cayenne is a rebadged VW. I believe 68% of the components are identical. My Lemony Touareg weighed more than my X5. Lemony Touareg V6 got way less gas mileage than X5 4.4i. The low range was great off road but who gets to play Paris Dakar every weekend?
I drove the Range Rover Sport...IMHO they should not have borrowed all the knobs and buttons from the LR3...and the rear overhang is bit strong; it has more cargo space than the X5 but does not have the feel of the X.
It is also slower 0-60 and get less mpg than the X5. Low range is great but I hear that you can disable the DSC on the BMW and have a great off-road vehicle

...Also, just like the Range Rovers, the X5 has descent-control. And, from I believe 2001 through 2004, when they were owned by BMW, the Range Rover used the BMW motor.