My buddy just bought a 7.3 after driving Cummins Dodges since the 90's. He's happy with it. He said it was nice not worrying about fuel gelling going up north. He said they got 9 mpg hauling sleds.
We drove a Duramax a couple weeks ago and only got 10.5 -11.5 towing 3 sleds in an enclosed trailer. It was cold and windy, but that sucks. We also threw codes coming home and it said it was going to derate to 65mph then 55 then 5. It didn't end up doing it, but it was unnerving wondering if we were gonna make it home.
There are a lot of factors to consider in the diesel vs gas debate. In my mind the biggest thing now is all the emissions stuff and all the unreliability with it. DEF heaters and DPF's are expensive to fix. And you can rack up some repair bills when they start throwing codes. Not to mention getting stuck on the road when they go into limp mode. Oil and fuel filters cost more too. I realize the diesel option is 7-10k but that usually pays off in resale value. It will be interesting to see if that continues. There is undeniably more power out of the diesel, the question become whether your loads and terrain need the extra power.
The diesel will require two batteries, which need to be replaced about every 3 years. It may require the cab to be removed to work on it. The gasser doesn't need DEF and anti gel additives. It's easy to find gas stations. It's hard to debate the fuel price, diesel used to always be cheaper, but lately has been higher until just recently (at least here fuel is cheaper right now).
My 2011 6.7 ford is deleted and gets 13 towing (5th wheel camper, skid steer, 40ft featherlight gn) and 16-18 unloaded highway. With that said, I don't have the camper or the gooseneck anymore so I really don't tow big loads that often. I will be looking at the gasser when I purchase next. Especially since it is getting pretty difficult to delete anymore.
It appears that the emissions failures/issues has already adversely effected the prices/values of the used diesel pickup, light truck market. This came directly from a dealer salesman, who is very sharp minded on truck specs, and price values. Perhaps what comes around, goes around, eh?