I have seen some debates on this. Typically someone is asking which is more realistic.
The answer: Neither.
If you want realism in your game, then you'd have a hit location chart with severe consequences depending on where you got hit. The number of push ups you do that morning or your healthy diet won't make a lick of difference to a bullet that impacts your cranium.
The argument stems from the misconception that these systems are trying to model realism, when they are really trying to model fiction (literary, comic book, pulp). Why? Because they bend the laws of the universe to give the hero a chance. And because it is a game.
In a real firefight there is a very good chance that the hero will be killed or permanently disabled with a single bullet. That wouldn't be much of a story. What would Star Wars be if Luke had suffered major brain damage from the Tusken Raider's attack? I bet Obi Wan would have wished he had started training him earlier then. Besides, Reality is just the cage we build for ourselves.
The current RPG damage systems give you a second chance. Wham! A shotgun blasts you in the chest, but your still alive and can change tactics (or roll better). Why? Because it is a game. Because checkmate in one move is boring for both the players and the audience. Because the Quiddich ball game is pointless if catching the Snitch is all you have to do to win... oh.... umm...
So which is better? Depends on how they are handled, and personal taste.
I dislike D&D style hit points because your character gets healthier with higher levels. In fact, going form 1st to second level doubles your hit points. And don't try to give me some BS about it reflecting your fighting ability because we already have armor class and Dexterity isn't adding in to hit points, Constitution is.
I prefer games where the hero's general health doesn't increase unless he's done something to earn it like changing his diet and exercise (attribute bumps). Even then, the increase should only be minimal.
It's one reason I like Savage Worlds Toughness but I have also seen it done with Hit Points in Cortex Classic (Serenity, Battlestar Galactica, Supernatural RPGs).
I also dislike games that offer no penalties for injuries. In D&D I fight at full potential until I reach 0 Hit Points. Then I guess I suffer a heart attack or something. Gee, I looked so healthy and virile, having a good time... and then I just stopped.
So I guess what I'm trying to say is, why bother modeling a game on reality if you have to use your imagination to play it? Go outside. I hear that Outside is chock full of Reality, in an expansive 3D multi-player world. Just be careful, I hear the player base is full of Trolls and the tech support is crap.
BTW sorry for the late post. E3 is coming up so I'm pulling 11 hour work days. It's cramping my free time.
