Both will pull it fine. The 35d may do better on towing fuel economy if you are towing a lot and that matters in your case.

Engine torque doesn't much matter, for all the press it gets. It is hp that gets you up the hill at a given speed. While the diesel has good low end torque, so does the 35i, it is a characteristic of the turbos more than the combustion cycle. While the diesel has higher peak torque, you are fortunate to have a transmission so wheel torque will be higher on the 35i than the 35d, at a given speed.

Does your 35i have the 8 speed? That would matter more than the engine, to me at least.

Short story, whichever one makes the most sense for you.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
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