My Benelli has been great to me so far. I'd run the M2 and not worry about it. Folks run anything from 24" up to 28" for barrel length around here. The guys with the 28 inchers are typically using them for duck/goose guns as well.
I like a full or extra full choke when chasing the long beards. Try a couple if you can and see what produces the best pattern.
Good luck.
