Same shot size you use in 12ga. Im not a huge shotgunner but the reason for a 10 is to make the shot pattern more dense at much greater distance. Its not going to make you a better hunter just makes it more liekly a killing pellet hits the bird at a greater distance.
The ammo is pretty pricey especially if your hunting a no lead zone. Its a major reason you dont see them very often even in goose hunting. The advantage of the dense pattern doesnt really offset the abuse your shoulder takes or the higher cost of ammunition.
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." — L. Neil Smith
The problem with being stupid is you cannot simply decide to stop doing dumb things...
"I crapped my pants to avoid the draft!!" -Ted Nugent