Yeah looks like |I will have some reading to do here to catch up on all the issues. I wonder who came up with the 270 under bore rule for coyotes etc. What happens if you are hunting wolf and deer....
Why 20 over a 12 ga - are you thinking for recoil? The only time it would be really noticeable is sighting in. I find I don't really ever notice when shooting at game. Hunted with 338 win mag and 45/70 so should be fine. And of have fired slugs off in my 12 ga. Will think about the 930 - have heard there are feeding issues with the 535.
20 gauge guns are generally lighter, and less bulky. Much nicer to carry around, and doesn't give up much in terminal performace.