I went with a 3500 gasser this time. This motor mated to the new 10spd is a performer. I went 3500 gas for most payload. I don't tow heavy everyday, but I do haul. I drive a lot of stop and go back roads. If you're driving highway, just get on it (duramax) here and there to keep it clear. Hwy mileage I'm getting 16-17, but backroads 10. Not sure how the diesel would do with my driving habits. If I were towing/pulling heavier trailers more often, I'd go diesel. In the end, sounds like you should go with the gas though. I absolutely love driving this big Ole beast.