28............20
For about the last 15-18 years I have hunted mostly pen raised pheasants over a GSP. Almost exclusively with either an AYA side lock sxs 20 ga. with fixed ic and mod chokes, or a Ruger red label 28 ga with screw in chokes. After several hunts with each I did quite a bit of pattern work. I knew my first shot would be close, 20 yards give or take, and the second would usually be in the 35-40 yard range.
1 oz. # 6's plated in the 20 ga. worked best. The 28 caused me more time and experimenting. Finally I settled on 3/4 oz # 6's in a skeet choke and 1 oz #6's out of a mod. choke.
Over the years with 30-40 pheasants average per year I saw very little advantage for either gun with one exception. For some as yet unidentified reason I kill longer distance birds better with the second shot in the 28 ga. than I do with the 20.
Even with that result I only favor the 28 if it is raining. Not because it has any advantage, I just can't beat up that AYA.
For clarity, I only hunt birds with these two guns. Mostly pheasants, second…Quail, chucker’s, and grouse. I do not shoot sporting clays or any other targets.
And, I'm more of a snob with the AYA than I am with the Ruger 28 ga............................