The 410 is a very over looked round.Power wise they're comparable to a .357 (if i remember correctly) .The two big issues for me though are the effective hunting distance (when using shot) and also the scarcity of the 410 if you need to scavenge to re supply (the same reason i sold my 20 gauge) They're also bloody expensive,I used to have a 410 Enfield and feeding it cost an arm and a leg,it also got some funny looks at the clay ground
If using shot you're really restricted to 25-30 yards as the cartridge just doesn't have the space to hold enough shot to guarantee a clean kill beyond those ranges (lots of open holes in your shot pattern ),and the 410 can have a tendency to string the shot so instead of an expanding disc of shot you get a string.
For me slugs are the way to go with the 410 (for UK defense) and I wouldn't feel undergunned
My biggest worry though is resupply.Where I live the 12 gauge is king and every farm has one.If and when i ran out of ammunition I would have a much better chance of scavenging more cartridges as the 12 gauge is the most common type of ammunition in blighty.Of course you have the problem of increased weight and less ammunition you can carry.
If I had the spare cash I would splash out on a Bretton Gaucher 410 and 2000 cartridges with a slug mold tucked away just incase.
The 20 gauge is a fine cartridge but again it's just not as popular as the 12 so resupply would be a problem.
It's all a trade off.For me despite it's weight and size the 12 gauge is what i've opted for,but if/when i have the cash I wouldn't say no to a silenced 410 and lots of cartridges. The Bretton Gaucher is silenced with a cylinder bore and can be fitted with a scope (the French use them for slug hunting)
Getting back on topic I just missed out on a .45 smoothbore Hawken reproduction with double set triggers.Gutted