You'd like to get 3.92's to get better in town mileage... Really can't see that happening. I've had two 2019's, the first one had 3.21's and my current one has 3.92's. Definitely got better mileage with my first '19 with the 3.21's, and that truck even had the Off-Road Pkg. You could buy a LOT of gas with the money you'll lose driving another new truck off the lot. If it's primarily about changing the color, that's a different story.
I traded to go from quad cab to crew cab, because I got a company truck & no longer needed my truck for work, but needed the back seat room of a crew cab 'cause the truck was now going to be used as a "family car" instead of a work truck, so my needs changed. My crew cab has the 3.92's and I don't like the low gears to be honest, miss the smoother, more relaxed feel of the 3.21 setup, and the lower RPM's on the highway. To each his own I guess. I do not miss the firm ride of the first truck with ORP, rode like a 3/4 ton truck in my opinion (and I've owned lots of trucks in the past 35 years). Put over 20,000 miles on that truck with ORP and I don't miss that package one bit for highway driving. Noiser with the AT tires as well. All the talk about the "buttery smooth" ride of the Ram trucks made no sense to me until I got rid of the truck with the ORP and got the standard suspension, now I get it.
If I traded again, next one would have 3.21 gears, Ram boxes, and split tailgate. Other than the split tailgate option, I can't even think of any other differences on the '20's vs the '19's..