The lighter recoil ammo, that is now available for the 12 gauge, duplicate the 20 loads so closely, that there's probably not as much motivation to use the 20 as previously.
I was thinking about switching to the 20, too, but the 7/8 oz loads for the 12 gauge feels exactly the same, without having to buy a new gun, (not that having to buy another one is a bad thing).
Since the 12 is a little heavier, there's actually less recoil than with the 20, too.
Walt Kelly, alias Pogo, sez:
“Don't take life so serious, son, it ain't nohow permanent.”