Depends on why your using a shotgun I guess. Many of us don't use them because we feel it's a challenge, we use them because we have to. Many states don't allow rifles so you either use a slug gun or muzzle loader. Both of which I personally will use a scope on because they both have usable ranges up to and beyond 100 yards. I normally go for low power scopes on a shotgun though, like 1.5-4 or something like that.

If you don't plan on taking shots farther than 50 yards or so or if you good with open sights out to 100 then there is nothing wrong with a nice quality open sight over a scope. Really depends on what your more comfortable with. I actually prefer a scope myself to be honest. I scope pellet guns for crying out loud.

Paul