"I think the X6 drive, suspension and chassis components are basically identical to the X5, so I wouldn't expect any notable differences between the ride and handling of the two models (assuming they were configured with the same options)."

There is a noticeable difference in handling because the two chassis are not identical. Although they are almost identical, the X6 has always featured the active rear differential, which sends more engine torque to the outside rear wheel to literally push the car into a corner. Acura offered it first as "Super Handling All Wheel Drive". Audi now offers it, as do Porsche on almost all models including the 911.

The only X5 which has it is the X5M. Its avail. on the new X3, so I'm sure it will be on the next X5.

But make no mistake the X5 drives like a really nice truck, while the X6 drives like a trucky car.