I also drove the Cayenne....
When I was ready to upgrade from my previous 2001 X5 4.4, I went to drive the Cayenne (S not the turbo) and really wanted to like it. I have had 4 Porsches over the last 15 years and love the cars. I was very disappointed in the quality and ride of the Cayenne. Things rattled, didnt work right and felt really cheap inside. I kept it for the weekend and couldn't wait to return it. I ended up ordering a new 2004 4.4 X5 Sport and have not looked back. I can't speak for the Twin Turbo, but the S is no comparison to a properly configured X5 4.4.