Recoil is a function of weight of the charge, velocity vs the weight of the gun. More lead, higher velocity , lighter gun equals more recoil. Recoil could care less if it generated by a 12 or 20 gauge gun. Go with the 12....you can shoot loads down to 3/4 oz at 1100fps or lower, if you want. I shoot 7/8oz at 1125 out of my 12 gauge Smiths and the recoil is very light. A load of 1oz of number 6's on the head of a gobbler will be "lights out". Lighter loads generally produce lower pressures, a good thing for older guns. The best solution to you problem is to buy them both. Trap and turkey with the 12....quail with the 20. This will make you happy.