i use 2s for smaller canadas and snows. ive shot 100s of patterns with different shells, and i think 2s is about the best. lots of bb pattens get pretty thin for small geese. A good patterning bb shell will have 65-70 hits in a 30 inch circle at 40 yards, where as a good patterning 2 should be around 110.
Youd be surprised how many guys use nothing but 2s all a round. They do just fine on big honkers. I swear they slip through late season feathers better. Just a lot less feathers pulled into the holes than bb.
Split the difference with ones. Snows come down pretty easy. Pattern your gun, you would be shocked what a different choke can do, non ported choke generally do best with steel.
Smaller shot give's better odds of head and neck hits!
Both will be fine in most situations. If you are going to be shooting inside 50y 2s are good, if further than that BBs are probably better. Extra points for hevimetal but more $$ over steel. Snow geese fall pretty easy so there's no wrong choice. I shoot BBs all the way up to 5s as I usually burn up any leftover ammo on snows