Since you have an offroad toy, get the Cummins. Filters/oil cost more, but the extended service of them make it a wash. Fuel mileage will be greater, and depending on where you are in the country diesel will be just under or just over the cost of regular unleaded. My wife's '14 Durango with the 5.7L Hemi and 8sp auto gets 1.5 mpg less than my 9,200lb Mega Cab dually Long bed conversion around town. Her Durango is approximately half the weight of my truck, so the Power Wagon will get even less. Granted on the highway unloaded she gets better economy. With a trailer though, fuel mileage goes down drastically with the gasser. When we moved to GA from AZ, the Durango and my Cummins got identical mileage on the road trip. She was pulling a uhaul trailer, and at about 8,000 lbs combined. I was at 20k combined. None of this takes into account that most of that trip I was chugging away at a fraction of her RPM, particularly going up the (few) hills.