Its been established a long time ago that your performance gains become less as you increase the column of shot in a shell beyond a certain point. I believe the 3 1/2" is in this category as I don't see too much performance gains from using a 3" over a 2 3/4" shell on waterfowl. The 3 1/2" round was meant to do what the 10 guage does, but it really doesn't. If you need to put more bb's in your shells, go with the 10 guage.

Alcohol, Tobacco, and Firearms... who's bringing the chips?