If you use a heavier load than the ones I was using on that shoot, the M3 should do OK. I haven't had any problems running game loads (usually Remington) through my M1s. Those also have magazine extensions offerred from Benelli to increase to 7+1, or if you go with the Practical, even more.
The Remington I have has a 28" barrel and a Choate extension that increases capacity to 9 rounds in the magazine. You can, as I did, do a few minor things to increase it to 10 rounds. A potential weakpoint of the 1187 is that it is gas operated and the O-ring can (and will) eventually fail needing replacement.
I haven't tried Winchester's Super X2,......yet. A Super X2 Practical MkII is on my list, though.