IMO, gauge is one of the last factors needing consideration. You have to get to heavy loads before the 20 won't do it. BTW, gauge has nothing to do with recoil other than 20 gauge guns are more typically lighter in weight which means more recoil for the same load. 12 and 20 gauge guns both come in wide enough variety you should be able to find one to suit your needs with no regard for gauge.

DDA