hmmmm
Having them both solves the problem (if there is a problem). With a limited budget, though, the OP is not buying both.
I have both - as do many of y'all - but I shoot the 12s more.
About 20s and Trap. Yes, you and I may meet the fellow at the Trap range who can consistently outshoot us with his 20. (The other day, I had my 20 gauge O/U at Trap and shot it as well as my 12). One or two examples do not a proof make. The big money winners, as far as I know, shoot 12 gauge.
Pete