Now this is a pretty interesting thread. It's usually always the whole 12 vs 20 arguement. Nice to see something new. As far as a 28 gauge goes I pretty much have no experience with it. My first shotgun was a 12 gauge. Now as far as a .410 goes I really don't have much experience with it reguarding slugs or buckshot. The slug experience was pretty impressive. Them rifled slugs do great from the smoothbore .410.
If you want a truly impressive .410 HD shotgun you ought to try shooting a 3" .410 shell out of a .45LC derringer.