A 10ga is not over kill to say, I have an SBE, 10 O/U and had a SP10. I like my 10ga O/U for turkeys, ducks and geese. If you are a good shot you can kill all with a 3in 12 ga but if you need a little help with extra steel then the 10 ga is OK.
Heck I even shot dove this year with #6 10 ga turkey loads.....that was a blast!!!!
It all comes down to what feels good to you and what you can shoot accurately....