HBO Arm Length

[Taeth]

I completely disagree. What the HBO "arm-legth" measure measures is who has the edge punching the other guy's shoulder. WHO CARES! The single most important punch in controlling distance (perhaps the single most important step to winning a fight) is the jab to the head. So the distance across the shoulder (ignored by arm length) matters a great deal. REACH is the far better measure in demonstrating that.

Of course the best might well be the distance from a closed fist to the side of one's face when facing forward.

The other issue I have with it is, as a history buff, I have no way to compare "arm-length" of a current fighter with fighters of the past. But that is a seconday point.

The only thing that is covered by reach that isn't by arm length is the distance between the shoulders which doesn't matter at all except maybe fore power. When you reach out your arm the shoulder is fully extended in any direction, like a fully extended punch except maybe further because the arm is completely straight. ANything to do with shoulder extension is encorporated in arm length.
But like you said later, all that matters is where your feet are. Pacquiao has a tiny reach by either measure, and he fights at a distance better than almost anyone because he moves in so much and commits so fully to his punches.

That's just not true. The distance between the shoulder and the face is ignored. Those inches are as critical as any other inches unless you think the jab to the head isn't the most important single punch in boxing.

The only reason the jab is most important punch is because most people don't know how to move in with any other punch. It's more of a footwork problem than anything, and that's because boxers only watch other boxers to learn footwork and not other forms of fighting.

You can't take into account the distance from the shoulder to the face because nobody who knows anything about boxing stands perfectly sideways against an opponent, and the doesn't come out in that wingspan type posture. The only thing that matters is arm length. The way you would have to punch to utilize that distance between shoulder and the neck would be a berto type backhand jab.