I have a SX3.
I shoot 2 3/4. 3 and 3 1/2. I also pull out my 10 gauge every now and then.
2 3/4 = 45 % usage - Duck and grouse
3" = 40 % usage - Duck and geese
3 1/2 = 15% usage - Canada Geese only
2 3/4 will kill a goose when they're close but I prefer to kill them dead. 2 3/4 gets you some cripples.I have made some long shots on Canada Geese and they were all from 3 1/2 Blackcloud #2. Reason for long shots, too many hunters out there that don't know about cam and concealment, keep scaring the waterfowl high, need to make some long passing shots.
There is an old saying; rather have it than need it than need it and not have it.
Use what you need to get the job done.
As for kick, sore shoulder, ha, keep good contact with the butt and you won't have any.
Wouldn't need to use 3 1/2 if I used lead and not everyone can afford Hevishot.