#2 lead, in 1- 5/8 oz loads used to do it for me every time, for geese in the days of lead.
Ive tried Bismuth and it was ok, but pricey.
I've tried heavy shot on ducks and geese and was totally impressed, but they were pricey.
So, Ive settled on steel in BB for geese, on body hits inside 40 yds.
Still not impressed.
There's so much to be said about steel shot, and none is good.

It goes out fast but slows down sooo fast, that at impact it has no real kill power and leads required at 40 plus yards become ridiculous because of diminished energy.
I'm gonna settle on #5 hevi shot for ducks and geese. Same as # 4 lead, and penetrates goose breast right through into the vitals.
Not even a question on pass through hits on ducks.