You can use buckshot in Maine too. I am not a fan of buckshot, I think it encourages a hunter to be careless in his aiming. A lot of deer end up wounded and not ever found. A lot of buckshot entry wounds bleed very little, which makes tracking very difficult, and sometimes impossible.
I have also had my experiences with both single o and double oo. If I use a shotgun then it is slugs only.
My dad once told me, that him and his brother, and one other person slammed a buck so many times with buckshot before he finally succumed, that the deer wasn't even worth bringing home, because it was peppered with buckshot.