HEHEHE!! I guess it was at the last shoot I was at, as I was poppin the shotgun poppers I heard someone ask, "Is that black powder?". The reply from the "seasoned vet" was "Yep, lot's of smoke and boom but almost no recoil", well needless to say I took that as a personal challange!!! A little later in the day, I had the "vet" try out my little 20 ga. It's a sweet little Browning SxS, weighs about 6 lb. swings great and shoots sweet! Anyway, I slide a couple of shells into the gun for him to try. Well we won't hear comments like that from him again!! 80gr of FFF under an ounce and a quarter of shot in a 3" mag shell from a 6 lb gun will get your attention!!!
Yep, most 20's are lighter, therefore more felt recoil, generally, but it doesen't have to be that way. You'll probably have to reload your own, but they can be loaded really light, almost to 28 ga feel. I won't give up my 20! I'll just load'em different for folks that are recoil sensitive.
As an additional thought, BP does give a little more push as opposed to thump.