Its unfortunete that you only get the X5 35d in the US to compare to Cayenne, when the X5 40d actually gets better miles per gal.
I have had the X5 30d, X5 35d & now the 50d, all my X5's have had the same options, but the 50d gets much better economy than the 35d. My average of 80% city driving & 20% country gives me 9.4ltr/100klm, and l am not a light footed driver.
The Cayenne here has an option of a offroad pack as well.
X5 F15 M50d White, 20"rims, Yellow Calipers, Ceramic Pads. Better off saying what it does not have and that's a B&O Audio System, other than that every option box is ticked.