FWIW, while I can't speak for any later model years than 2019, I've had F250, F350 , and F550. Anything is better unloaded than the F550, btw. :)
I've never noticed a huge difference in unloaded ride between the 250 and 350 series. Bit more squat on the 250 if the two were equally loaded. I tend to follow the #'s, so didn't have too many direct comparisons with either fully loaded.
My current F-truck is the 2019 F250. After circa 60,000 miles (40-50% towing, although not an RV), my only regrets are: a) that I didn't get the F350 (at the time it was an extra $1500); and b) that I didn't get the 8' bed. No reason for wanting the F350, but in hindsight, the slightly higher ratings would have been worth the $1,500 to me. The 8' bed was a wash price-wise...could have got that for the same price as the 6'- 9" bed since no one seemed to want the longer bed...but nothing was in stock and at the time is was an estimated month to six weeks out. ...hindsight provides lots of reasons for the 8' bed, I kick myself for not waiting the extra 6 weeks.