Owned them both. The 35i is quicker and feels more responsive overall to me. The 35d does offer better gas mileage, around 2-3 MPG for me. Once I factored in the extra cost of diesel and remember I'm buying a 60K SUV, the little savings in fuel didn't mean much to me.

I also love the sound of the 35i.

That said, there are 35d lovers out here and I sure don't disagree with their love of the 35d. It's a personal decision. Some people like to tow and the 35d is a much better match for that.