Hook a real trailer to them and run them up a real hill and the new trucks are are all within a couple mph of each other with the pedal to the floor. Gas or diesel.
Gas or diesel should both last 200k or better long past when most are ready for a new truck because they want something new.
Many prefer the towing experience of a diesel and there is reason for that. However there are also downsides to the diesel experience. Fuel IS harder to find. not ever station has it, those that do usually only have one or two pumps that might be occupied blocked or not in a convenient location to pull your trailer to. Also something that is important to me is that many diesel pumps around here don't have a pay at the pump card reader, I can't stand having to go in the store going in the store to pay would drive me far crazier than a small block running 3800 rpm for 7 minutes going up a hill at 60 mph.
If you want a diesel get one, they probably are "cooler" than a gas truck. But I just wish everybody on this board would stop telling guys towing an 8k lbs trailer that they NEED a diesel. A new gas truck will pull 8k lbs at the speed limit up every interstate grade with the exception of maybe a few of the really high altitude ones.
It isn't made because the abysmal fuel economy but if someone made a 6.7 liter direct injected turbo gas hd truck engine it would blow the doors off the diesel trucks in any measure of towing performance other than mpg. It would also have the low rpm torque that a diesel has.
Diesels big advantage is in mpg not performance.