Agreed 110%!!! ben is bang on! It's why I run with a 3.5 inch chambered 12 gauge!
Again, bang on! pacobillie has it!!!
I'm gonna take a guess that you're just a better shooter than your buddies & you drop birds more effectively with the 10 ga as a result... (A compliment, even though I don't agree with your saying the 10 ga is a better waterfowl gun...)
I'll finish by saying what I have been saying for the last little while... I used to use a 3 inch shell with #4 steel going 1550 fps, dropped ducks like nobody's business... Switched to a 3 inch shell with #2 steel going 1550 fps for geese...
Started getting into more & more geese, so 'being prepared' for a mix of geese & ducks soon saw me going to a 3.5 inch shell loaded with #2 steel & going 1550 fps. This allowed me to be ready for ducks or geese & has become my go to shell for waterfowl in any situation.