I have the GMC version of the truck GON is talking about and agree with his observations. Anyone who thinks the 6 speed is deficient doesn't own one. We have over 6000 miles towing now and the transmission does it's job with no drama. Would 10 speeds keep it at more optimal rpms? Of course. If you needed a truck in 2021 it really didn't matter that they put a 10 speed in it in 2024.
We ordered the truck because at the time used prices were spiking availability was poor and it make sense. I discovered while configuring the truck on the GMC website that a 3500 was just $400 more than a 2500 instead of the usual $1200. It was a pricing quirk and since the only differences are an 11.5 rear diff and overload springs added to the rear packs I got the 3500. Rides exactly like a 2500 because the truck has to squat 3 inches in the back before the overloads engage.
This truck was built 4/21, right in the middle of the chaos and the only flaw was a small clunk in the steering that has a TSB for the intermediate steering shaft. It's a GM thing, I had a truck in the early 2000s with the exact same clunk. Not a saftey concern, a tolerance stacking thing. The truck tows like a boss and has enough capacity to go bigger if we want and we didn't pay the $10k diesel tax.