The S&W ribbed barrels look pretty neat for one thing. On the practical side, one doesn't have to put as tall of a front sight or sight base on the gun. It provides for more sight base options. Can be used as a sight base by milling it out on top and pinning through the side. The rib adds some weight to the barrel for balance and help with muzzle flip like a underlug does. And did I mention, that it looks pretty neat?
In the picture is a couple of Bowen Single Sixes, one with a K-22 barrel on it. Complete with the original front sight........Not mine.