I'd just like to say, that I am thoroughly enjoying watching people talk about stuff they probably, when it comes right down to it, have no real idea about.
Now, proceed.
By the way, the pillum was more of a javelin than a spear, correct me if I'm wrong of course. Made of soft metal so that it would render the opponents shield useless.
Get in close with a dagger and you win.
If it was used to throw, the momentum would almost always make it break off in the opponents shield, and yes, it was designed that way. When used in battle, that was always the goal, but it didn't always work that way. The gladius was long enough to reach past your shield and into the opponent, but if you're in formation with an army, a dagger is not what you'd want to use. In order to make it an effective weapon, you'd have to break formation, which was a tremendous advantage. Otherwise every army would have used daggers in battle. They didn't. There are very good reasons for that.
In one on one combat, there is also the law of diminsihing returns. My favorite weapons is a sword somewhere between the length of a broadsword and that of a short sword. It doesn't put you at much of a disadvantage with opponents with heavier blades and it still gives you reach, plus its lighter. If the blade is too short, the required skill to use it effectively goes up faster than the inherent advantage the extra speed would give you. Also a smaller weapon becomes primarily a stabbing weapon because it's not heavy enough to slash against an opponent with any sort of armor. To use a short sword against an enemy with a longsword requires you have to know what you're doing and play your advantage against his disadvantage. To win against the same opponent when all you have is a dagger, you have to be better.
On the other hand, it doesn't take much skill to be dangerous with a polearm, except the problem is you're a danger to most people around you and probably yourself if you don't know what you're doing. It's fine for an unskilled fighter to use a spear or pitchfork to keep a wild animal at bay, but it's quite another to try to defeat a warrior who knows what he's doing.
I'm no expert. I expect someone who's good with a dagger could wipe the floor with me, but if he's an expert in knife fighting and has never run into anyone with a sword, I'll probably wipe the floor with him, because I HAVE used a sword against a knife.
Idoru: The pilum didn't have a barb on it, but it was designed to snap when thrown and usually did even if you missed. I suppose an enemy could have used the end (which was around two feet give or take) but it wasn't going to be as effective as the weapon they already had.
On the subject of experience, no I've never duelled to the death in RL, but I've had plenty of brutal experience with the advantages and limitations of a wide variety of weapons. I have the scars and memories of nasty bruses to punctuate that experience. I've used pole arms, swords, maces, axes, daggers, shields, worn a suit of plate armor in battle (although I've never rode a horse in one) fought with and without a shield, used two weapons and one, been in knife fights, one on one, wild melees, ambushes, battles with tactics and strategy and I know a little Akido. I've fought opponents who know fencing (florentine which is actually a very good style) and competition fencing (which isn't) Kendo, Karate, Akido and used and had used against me a variety of unclassified weapons (including a rather ingenuous two bladed dagger designed for throwing)
As I said, I'm not an expert (although I have been up against experts), but I do know something of what I'm talking about.