Id much rather shoot a 20ga than a 12ga. If I had found a good deal on a 20 before I bought my 12ga, I would have bought it. I think for dove and quail hunting, as well as busting clays, the difference won't be much. It's a little less shot, sure. But I doubt you notice too many more misses than now. I'm not sure about duck loads for the 20ga. Never been a duck hunter.
The very atmosphere of firearms anywhere and everywhere restrains evil interference. -George Washington