If he's patterned HIS gun and knows what THAT load in HIS gun is capable of, who are YOU to tell him different?
Yep, out of a .680 turkey choke, for coyotes
Who are these "most"?
#4 Buck is perfectly acceptable for defensive use, and is preferable when an overpenetration concern is present. It is the smallest that is considered effective, but it is universally considered effective.
Is #1 or 00 a better penetrator than #4? Absolutely.
Keep that in mind if your neighbors walls are close to yours.
#4 is "universally considered effective"?
By whom? There is not a single LE agency that I know of that specifies #4 buck. And for good reason: it will not reliably penetrate enough to reach the vital organs, and thus cannot be considered a good enough stopper.
And, as for your over-penetration argument (which is pretty stale at this point): As Old Painless so aptly said, "But doesn't 00 Buck penetrate too much in interior walls to be a "safe" load in a home?
Yes, it does penetrate a lot. But any load that is going to be effective will need to penetrate walls to have enough power to penetrate bad guys. If our only concern was to be sure we didn't penetrate walls, we would use BB guns. However, BB guns will not stop bad guys.
Therefore, we must use loads that will STOP bad guys, and this means that they will also penetrate walls. So, be sure you hit the bad guy and do not shoot into walls where loved ones are on the other side".
An unscientific statement by the guys at box of truth that #4 isn't good enough because it only went thru 3 milk jugs instead of 4 is useless and irrelevant. They are entertaining, but very seldom a valid source for citation as experts. Firearms Tactical makes a summary of other's work. But if you look at images of #4 penetration in gel, you'll find that 11-15" is the standard, not the exception. I've witnessed gel penetration tests of multiple rounds, calibers, and gauges in person. I've seen nothing to make me think that #4 isn't enough to get the job done.
Sorry, but I will trust my own observations, over a period of nearly 40 years, as to the effectiveness of various loads for HD, as well as the reports of reliable organizations, such as the Firearms Tactical Institute, the FBI, and various LE agencies, over your observations.
Choices like this need to be made on each individual situation. A sweeping statement that 00 or #1 is the best isn't universally true. Fred stated his front gate is 51 yards from his front door. Some people can't shoot 50 feet without hitting a neighbor. Think those situations require the same ammunition considerations?
Circumstances can certainly dictate the choice of ammunition.
I only use LE132 00 and LE132 1B because I want every pellet to hit the target, and those loads (along with LE127 00) are the tightest patterning, most effective shells I have ever used. In addition, both LE132 00 and LE132 1B are low velocity loads. In any case, at 51 yds, I will be reaching for slugs, rather than buckshot. Are 00 and 1B universally considered the best? I think that "most" would consider that to be true, and I don't think that can be said for #4.