It's the totality of the characteristics. The M1 and M3 shotguns started out as military shotguns that were later modified to make them acceptable for hunting purposes, so there would be a combination of accessories, which you could describe as appearance, but it has more to do with ergonomics for the shotgun. It's a combination of physical characteristics like the configuration of the stock and the configuration for the sights. Also, the tactical versions generally have a shorter barrel than the hunting shotguns, and they may have a larger magazine as well, so there are some mechanical differences between them.
On December 6th, 2022. See this statement in context.