Anyone got a 3500 Ram 6.4 Good or Bad?

Hey guys,
I'm contemplating purchasing a new 2017 Ram 3500 Dually with the 6.4, AT, 410 hp and 430lbs of torque. Anyone have one? Yes, NO, Good, Bad? On my 99 Ram diesel, pulling I got around 15 mpg give or take, Im wondering how much less a gas motor would be, 8-10 or so? If anyone knows anyone who has the 6.4 in a truck, please drop me a line or post a reply here. With the price of the new diesel duallys, I'm thinking I can spend less on this truck and just pay more for fuel.... what do you think?
Martin
Have a '16 4x4 that I bought for work. We pull a 13klb triple axel generator with. Does well. Little slower in the takeoff than the diesel but has no issue pulling it. I don't remember what kind of mileage it gets but am thinking around 12mpg on average. Boss has a heavy foot though. I will double check on that figure. Only issue that I had with it was not with the truck but the plow we out on it that did not like to interact with the headlights. Would up tossing thier control module and wiring in my own relay system. BTW. I orders this truck with 4:10's so mileage is definitely effected with them