I would have to go with the 3.5" nitro 0000 Because if you are going to use buckshot for defense I assume it would be a last defense and fairly close range (inside 30 yards) the 0000 pack a bigger wallop than the others do. They will also penetrate better than the rest and if you're going to bother to shoot it you might as well kill it also. What choke did you use for the tests? Play around with the choke if you can. My shotgun patterns 3" 00 better with mod. than full. Also where do you get 0000 buck shot? I've never seen it before.