I think an O/U without a top rib (even a solid one), just looks incomplete . . . of course that's just personal preference. I would also rather have a little extra weight on the barrel end via a rib as opposed to doing it via a longer barrel, but that's just the personal preference of someone who seems to make too many shots from deep in the bowels of a tag alder swamp.

"More important, we hoped that when Autumn came, the birds would fly"

-Guy De La Valdene