I drive a '22 one-ton SRW daily in the metropolis/city. I get 9-12 mpg depending, if Im flooring it or not. I get 14-18 mpg driving on the HWY, but I drive 75+ mostly. It can be bouncy (is the word I'd use) on terrible roads. I drove a supercar daily, so it's no different to me as far as harshness. Like my - former - STi I jump or blaze over all normal obstacles & hazards, but I get to also go over curbs in the 3500.
I dislike 1500s now and wouldn't ever own a non-HD truck again. When I was optioning a 2500, I was adding tow-hooks, locking differential, and couple of other options to make it more HD - which made it $200 less than a 3500. Therefore, I got all that and significantly more payload with the 3500 for a little more. Firstly, I was advised (here), because of payload, to get the 3500; however, I did have to research for myself, and they were 110% right.
I put two 4K loads of large rocks on a crate in the bed of my truck. I don't think it squatted at all, but if it did it was less than .25 of an inch. I got 9 mpg driving carefully home - all stop and go city. Its ride was smooth as butter under payload.
I have a Z06 and just got a new KLR650. Incredible gas mileage on both of them, but I always want to drive the "Big Easy" truck. I drive a one-ton daily and have other great options. I don't care about an extra few miles per gallon of a 1500 or the 1-2 a 3/4 ton would give.
At first, I didn't understand what all the harshness was about on the 3500. It took a pretty terrible section of road to understand what others were saying. YMMV.