I've killed geese at closer ranges with #2 steel, but only when I was duck hunting and had an unexpected opportunity. If I were specifically going after geese I'd use BB's.
Although more expensve some of the Bismuth and other non-toxic shot works great. Since it is more dense than steel you can go to smaller shot sizes such as #2's and do very well. If I were primarily a duck hunter and only rarely needed something for geese I'd strongly consider this route.