Nice dilemma !

I thought about it and finally went with an X5 35d.
Mainly because of the low end torque, and the fuel economy.

Daily driver to go to work, and I do fill it up once every 2 weeks.

What I do prefer about the diesel, is that I can floor it once in a while, but see little difference in fuel economy.

As I had an 335i before, I do love the 3.0 TT gas engine too !

This all comes down to your preferences...