For a defense load that is meant to kill the attacker and that attacker may be a bear the #000, which is heavier, and I have found it to group smaller. Since it is heavier, penetrates further (important) and larger It retains more kinetic energy per pellet, even if there are less of them. I like the #6 because of the greater number of pellets and denser pattern. In my mind a better chance of the "meal" being struck rather than slipping away by being in a "hole" in the pattern. I am thinking your "meal" may be nothing larger than a duck, squirrrel, rabbit or partridge. It's important they are struck and you recover them. Would you normally hunt those with #4 shot?....<><.... :grin:
As an aside, If what I were protecting myself against were men I might stay with #00 but more than likely go to #1 or even as far down as #4 buckshot. Defense only shots are taken at short range, long range and it's not defense but offense. With man targets disabling is enough, once they cannot use weapons and you can you are in charge. With wild animals you better kill them quick, if you don't they keep coming and they need no weapons to easily kill or maim you....And bu the way if you have never seen what a shotgun with #7 1/2 can do to a person a short range (a few feet) believe me, I have and it's not pretty, one big hole, just like a slug.... :cry: