Well...clearly both are English, and I'm sure this has been bandied about here before. It was a dilemma that I wrestled deeply with (first world problems, eh?) several years ago in my Don Quixote-like quest for the ultimate upland double. I've never fully-resolved the issue in that fate intervened and rather solved it for me. If the right 2-inch gun had come along before my W. Richards, I'd likely be having 2-inch 12-gauge shells shipped to my home and not 16, like this Christmas.
For me, it is the intersection of fit, weight, and lethality. Twelves (12s) kill stone dead for me more often than not, 16s come close, the rest....not so much. IMHO, it's a place where the 20 has little hope. Too light can be a problem (too-heavy isn't even considered).
