The 20 is a great gau. I use my 20 for decoying ducks , dove ,pheasants and rabit .If you can hit birds with it shoot it and don't worry. A 12 just throws more shot ,it's not how mutch it's what you bo with it ! For big ducks and geese a 12 is a big advanage, but if you are not shooting geese go hunting and have fun.