Well, if you go with the smoothie, you'll save a lot on slugs, and you'll also save on the cost of a scope and mount because there's really not much point. You won't be shooting much past 75 yds.
Even a rifled 20" isn't all that great past 100. Why not go for the full-on cantilever deal? Either that, or if it is a "dedicated" slugger, go with a Savage 210, or even an H&R Slug gun?