As a kid I tried a 410 several times, clearly saw the shot scatter around the bunnies, and the bunnies scatter into the bush. Nicely stalked, around 30-45' range (10-15m) I think it was #6 shot, just not enough pellets in it to have a chance of hitting one in the right spot.
By and large the few times I've fired a 12 gauge I've ended up with a similar opinion, unless you are poking it up the critters behind, then there's a good chance its going to get away, probably hurting, but not in the tucker bag at the end of the day.
I can see the value for trying something on the wing, but if its on the ground or water, near stationary I'd rather a rifle. Perhaps one day someone will show me how a 12g is supposed to work, but 12g, 20.3mm
10g, 21.4mm
8g, 23.2mm
4g, 26.3mm
that 4g is looking a lot more useful than below 12g. I bet they kick like a mule.
I've 5 bunnies in the oven atm, 60m-80m, would be damn hard getting closer in local terrain, 75m head shot gives a nice fuzzy feeling.