As you know I have an X5, but wouldn't have an X6. While I actually think it's an attractive car from the front (given the huge size and scale of the thing) it misses the point.
The X5 is a load lugger with 5 seats, refined compared to true 4x4 that are rather industrial and therefore a purpose in life as such. Knock it's 4WD all you will, but mine happily tows 2 tonne of Jeep across Europe, muddy campsites, and I can still turn up at corporate offices in it.
The X6 has only 4 seats, limited carrying capacity and iirc low tow capacity.