I grew up shooting 12 ga, so for me, it is a comfort thing. I don't notice the recoil from any of my 12 ga guns, and I can hit what I aim at 85% of the time, and that number is on a bad day. So I stick with it. I like to pull the trigger a lot, so cheaper cost for high quality ammo is another good reason for me to go with 12 ga, and has been most of my life.
My son and my best friend, both shoot 20ga. My son is 6 foot tall also, but at 15, not as stocky as I am yet. I know for him, it is a comfort thing too. I would imagine he would switch, if proven he could hit more birds with 12ga.
My buddy shoots 20 ga, because he cites the extra recoil from the 12ga as the reason for not using it. I think that is because he was using an O/U 12, and when he went 20, he used an auto-loader, so the kick dropped drastically anyway.
To each his own, I guess.
Class of '93 - proud Dad of a '22 grad and a '26 student!