While this is true, that it weighs less than a modern soldiers equipment, fighting in close combat with a sword is much more exhausting than firing rifles.
Even without armour, fighting in close combat is extremely tiring, I've done dagger-training (which is a medieval form of training with a wooden dagger to mark injuries), and after fifteen minutes where we were just wearing clothes, we were pretty exhausted.
Do this in an armour and it will be even worse. With proper stamina, you might get to being able to fight in a full plate for those full 15 minutes, but as soon as you have your visors down, you will become exhausted fast, as you cannot get enough air in.
Plate armored knights fought for three hours straight at Agincourt (Source: Juliet Barker's book on the subject)
But they probably fought in shifts.
Yeah I believe so too.
And what JaronK said too, in my belief the weather and terrain won the battle of Agincourt more than the longbows. Longbows had failed before on bright sunny days, without proper entrenching. But charging uphill, in rain and mud, against an entrenched foe, that uses horse-holes and spikes is a good way to lose a battle if I ever saw one, the fact that he doesn't need to engage you is just spicing on the cake, but I could be wrong, it isn't my main field of interest.
Yes, if you hit a naked man with a well place strike from your quarterstaff, you can cause severe trauma to him. If his armour is build properly, it will disperse the impact over a broad area, and then into the linen padding, which should absorb most of the damage. Yes, you would make a minor dent in the armour, but you wouldn't wreck it. That would take multiple blows to the same location.
Yes you can cause a major concussion of you hit the helmet. But hitting head and chest is the hardest when fighting against a man with a longsword, that knows what he is doing.
The entire chest plate of some of the later gothic plates where held up by one strand that was on the center of the chest. You wont be able to cut it down. Because when you go into one of your standard guard formations, you protect yourself from it.
Parrying so you make it into a glancing blow doesn't hurt a longsword much, it is pretty much made for it. Do it with a Quarterstaff, and some of the flexibility of it is already ruined. Yes a quarterstaff has better reach, however, most pole weapons have that too. They however have the added benefit of actually being able to deal piercing blows that can strike right through armour.
The way Longswords are held in the media, always at the handle is stupid. Yes you can start your guard there, but as soon as you get in closer, you'll have to adapt, and use the Handle and Pommel to beat you enemies.
The pommel and handle of a longsword are actually heavier than a Quarterstaff, meaning those would cause more blunt trauma.
However, if living in the 15th to 17th century, I would agree that quarterstaves have their uses. They are hard to parry with light swords, that get more common. And they are easier to learn.
Also, I agree that swim check penalties are quite insane, but so are the other armour penalties as well, unless a fullplate is really a plate armour combined chainmail with linen underneath (as used in the early middle ages).