I went from a '14 2500 with the 6.4L Hemi to a '16 3500 Cummins when we upgraded trailers. Pretty direct comparison.
I thought the 2500 with the coil springs rode really well, so I was somewhat resigned to a harsher ride moving back to a 3500 (had an older 3500 years ago). But it turned out to be pretty anti-climactic. Yes, the 2500 still rides better than the 3500. But the difference is pretty small on normal roads. Throw some railroad tracks or major potholes in the mix, and the difference becomes greater. But I seldom encounter those on my common routes. So I'm content with the 3500's ride. Just put 1300 highway miles on this weekend, and even my wife never complained.
If you're testing, break it out into two parts... normal streets, and some rougher stuff, like railroad tracks. That'll help see where the differences lie.