This is really just a random note that has been observed many times in the past, but I wish D&D had the notion of both a "difficulty to hit" stat and a "damage resistance" stat. Armor class, as one stat, models this poorly.
For example, a dude in plate mail is actually pretty easy to hit. Plate mail is heavy and restricts movement. However, it is hard to damage someone in layers of metal plates. Similarly, it is harder to hit a nimble dude in leather armor, but when you do, it takes less effort to wound him.
In the video game, Fallout, this is modeled well. There is nasty looking metal armor in the game, but it provides limited defensive value against energy attacks.
I am not proposing a system of damage resistance for OD&D. I am just lamenting the defensive model Gygax and company choose. It does have the advantage of being simple to understand, though.
UPDATE: Looks like OD&D artist and Villians and Vigilantes grandee Jeff Dee beat me to the punch.
Here's a snapshot of my desk, which captures how I play D&D these days:
