I am not a fan of the diesel (one of the few on this board). I am picking up a 35i to replace mine Thursday

For me, the diesel clatter is too much at lower speeds for a BMW. I am into the sports car type of sound. We also had some issues hunting down fuel on our last trip. It wasn't a major deal, just inconvenient and when we did find it the gloves came out thanks to gunked up handles. At 75-80 the fuel economy was good, but not earth shattering versus my old 3.0i. In Minnesota there were folks running into issues with DEF this winter if they kept their X5s outside (and the low DEF warning is really obnoxious)

Before I get torched, this is just my opinion. I'm more of a car type of person and not into messing around. My diesel has been reliable and as others have noted, it is excellent at highway speeds.

Right now, diesel is 36 cents more than premium in Minnesota. It has been higher since I bought my diesel. So I'm really not seeing any savings on fuel over the 35i. I will note that diesel was cheaper than premium in some states during my last trip out west.

Good luck with your decision.