If you're considering the diesel, go back for a second test drive. Leave it in drive, and accelerate around a corner somewhat slowly. Let it shift into second, then third. Then, roll into the throttle (don't stomp on it, or you'll provoke a downshift...just roll even pressure into it until you have about 80% throttle application).

This produces rapid, torque fueled acceleration, coupled with one of the sweetest exhaust notes around on a stock vehicle...which in turn produces giddiness and inappropriate giggling on the part of an X5d driver.