I have also dedicated this season to just using my 20.  I have been having shoulder problems(I think it is a torn rotator cuff) so I am using my 20 for the lighter recoil, but to be honest I dont think I can go back to the 12 now.  I love the 20 with its lighter weight and recoil and the thing patterns almost as good as the 12 does.  Its almost a no brainer for me.  Congrats to you