I was in your shoes a year ago. The reasons I went with gas instead of the D is 1. I couldn't get the Msport on the D. 2. Even though the D has a lot of torque, the gas is still faster according to BMW 3. Prem gas is about .50 cheaper than diesel where I live. I believe the new D's have an 8 SPD tranny now. As far as mpg I get 23 driving 85-90 mpg and about 25-26 driving 70-75.
It's good to be bad