Some really great thoughts on this subject.
I know many that shoot a 20 for pheasants and do really well. I for one like a 12 gauge. For me nothing makes me more upset than losing a wounded bird, I think that I owe the bird a clean kill.
I agree with the easy early season birds VS. the wily old veterans.
As for the pounding that your shoulder takes shooting those heavy load, people might need to look into a recoil reducer. The newer gas shotguns are the cats meow, I hardly feel a difference between a 2 3/4 inch 7.5 trap load or my 3 inch 4 shot magnum loads. Plus the more you shoot the more your body gets use to it, I shoot about 40-60 rounds of trap a year.
Not saying that it will make you a better shot though
Ron