If your seriously concerned with smoking range rovers go with the x5m. Maybe even have it tuned....I wonder what if any improvement in the already stellar 0-60 time could be had for say 20k. Comparing the full size rr and the x5 is apples and oranges. If you want performance get the x5 if you only require straight line pull but your taste emphasizes utility and luxury go with the RR SC autobio or whatever. Either way you will be a happy man as you do not strike me as the individual concerned with out of warranty service cost

And btw forget that rr sport its a hunk of trash. I test drove the face-lifted model as soon as it came out...thinking I would like it better than I did in 07...nope. Cockpit feels cramped which is not the case with the full size range and the seats are no where near as supportive as bmw's..also I have become way accustomed to my panoramic sunroof