Since this choice seems to revolve around the best all around UPLAND gun, and the poster stated a preference for a 16 or 20, and also with pheasants being added to the mix, then the obvious choice is a 16 on a scaled frame, no more than 6.5lbs. It's not called the goldilox of the uplands for nothing. 1 1/8 oz. 5's for phez and 1 oz of 6's or 7.5's for everything else, and you won't want to shoot anything else. The standard 7/8oz. or 1 oz. 20ga. payload with larger shot sizes is too slow and light for pheasants in my opinion.
