well if you are like me. I shoot to hunt. and in the summer months i have a thrower and practive on clays. thus said i began shotgunning with a 20 and have bounced from 20 to 12 a few times, and personally i have found that the 12 will give more reach, for late season when the birds are wise, and in my area at least it is hard to find the 4 shot, shells in 20, in no way do i knock the 20 i have one still as a back up, but i have found the 12 to be more usefull for me, on a side note i like to use the 12 because i have had a day or 2 where i have not brought enough shells, and as 12 is the most common, in my area, seems like my hunting partner was willing the loan a box to me. if i had been carrying a 20 it would have ended my day.