[AndreyATC]

Steve
You 're right, there is no technical difference in drivetrain and suspension
However, have you driven both, side by side?
You'll feel the difference between any X6 and X5 given the same trim and setup
The main difference here is the height
Lower center of gravity in X6 gives you THAT much of a difference
It's like driving one nice sport car for a little while and then lift it by 3 inch and drive it again
What do you think it would feel like?
People lower their cars by just 1/2 inch to gain some great handling capabilities
I'm not even going to go into other stuff that's different between these two, e.g. lighter wheels, geometry of the car.
Height alone is enough to make a lot of difference in performance, not just straight line acceleration

I hope this clears things up for you