I must say I have never driven the 8 cylinder X5. I guess I didn't want to spoil the thrill of the I-6 since I felt that over all the 6 would be adequate for my needs. I tried to be fair in my assessment of the ride and performance, as I wasn't looking to jump into an E70. I drove it for ~20 minutes on City & Hwy roads, the same drive I took in my 05 to get to the Dealership. The ride was noticealbly smoother and I honestly felt the engine to be more responsive than my MY05. I could not tell that I was pulling more weight. My 05 tends to lurch forward too easily upon starting from a stop. This one has a smoother throttle response. Engine noise seems about the same.