L5P engine came out in 17, still in production. The 17-19 models have the 6 speed Alison 3.73 rear gear. 20 & 21 have the 10 speed 3.42 rear gear, new body & chassis.
We pull a 12K fifth wheel, truck pulls it without issue. Where the 05 would just maintain speed, the 18 will accelerate. Should pull your 10K TT like it’s not there. We could have gotten a SRW 3500 truck at our weight, but would have been close to max weight with the load we carry.
Check the block heater, there was a recall. And some had the cords cut at the dealer before delivery. I never plugged up the 05, don’t expect to plug this one up. You can see it thru the passenger fender well.
I would expect the Duramax to use more DEF than your Ram, and the under hood fill is a pain at best. Real pain to fill from jug, I fill at the truck stop. Most hoses will reach, if not go thru the lane the wrong way or backwards.
The steering wheel isn’t quite centered to the seat. Bothers some, but to me it’s no biggie. Same with the lack of low speed throttle response. They just don’t jam you back into the seat, but once rolling they will produce plenty of power.
Ride isn't bad, but it's a HD truck. You get used to the rear fenders, but it's not my daily driver. (I did drive my 05 DRW every day some, but now have a company F150)