Mike,
In your question you defined the shooter as someone who would prefer a 410. I took this to mean that you were considering recoil for that part of the statement.
There is another relationship to consider that corresponds to the relationship of the bore size to the length of the shot string. As you put less shot in, the shot string decreases. As a result your timing have to be more exact. You could get to the point below 3/4 ounce in the 12 bore where it becomes too difficult to hit a moving target, but your patterns at a stationary target would look good.
Some ideas for recoil reduction would be slower brning powder, less shot, action that absorbs recoil and heavier gun weight.