It's hard to disagree with anything you said. Especially for me, since my knowledge of swords is very limited. But why should that prevent me from giving my own $.02?
I think it is pretty obvious that a sword, and particularly the traditional japanese sword, is and was designed and intended for use as a weapon, and it is its performance as a weapon, in terms of being easy and fast to draw and bring to bear, smooth and balanced to wield, effective in penetrating armour and inflicting injury, countering other weapons, and throughout it all surviving the impacts with minimal damage and maximal edge retention that really counted.
I understand that some swords were tested on cadavers and sometimes live bodies and sometimes notations were made on how many bodies were cut through. Some cut through as many as seven. It's difficult to test swords like this nowadays. given the relative shortage of real sword fights and the modern tendency to frown upon slicing through cadavers, prisoners or citizens of lower rank.
Now, obviously, performance like this has little utility or verifiability for the modern collector or the armchair samurai, although the balance and "speed" of a sword can be measured by practicing with it and some measure of cutting ability and edge retention etc can be tested against bamboo etc.
But even in Japan, the aesthetic qualities of the swords were extemely important, even to the point that they may eventually have become more important than actual "performance". Those qualities themselves originally were indicative of performance. The hamon and differential temper [and other features] was for impact resistance and the different shapes of the hamon were to minimize the extent of impact damage; the super complex grain structures were indicative of the quality of the metal and the forging etc., But the point that fascinates me is to what extent did the traditional arts of the japanese smiths and polishers become more aesthetic than functional? Would one of the great blades really be better, as a weapon, than a sword of the same shape and geometry made of modern steel and modern heat treating etc?
To me, there is no comparison to, say, a Masamune or a real wootz sword and even a copy made in infi or CPM 3V. It's like comparing a Patek to a Seiko. But I really would like to know , objectively and scientifically, how they would compare as weapons in terms of penetration, weight, resistance to impact, edge retention etc.
It is very likely that if these modern materials do perform better objectively, the old warriors, warlords and smiths who made the traditional swords and adapted them to perform better from time to time, would not have been slow themselves to use them in their swords, if they could have.
