This is indeed an interesting thread.
But we must be aware that historical facts are not black and white, such as "shields were made of X" or "armors wheighted X pounds". Back in the days before globalization, cultural interchange happened in a very limited scale. It is possible that a given tribe used such and such kinds of swords, and another, 50 Km away, used another kind sword or armor design, so an absolute statement about equipment wouldn't be reasonable. The reasons for the difference may be just aesthetics, tradition, availability of raw materials, quality of said materials, cultural preferences, origin of the merchants, etc.
Therefore I see no contradiction in saying that shields were sometimes made of soft wood, and sometimes of hard wood. Or that european knights used curved
and straight swords.
I just like to think that nordic warriors were, in general, better fed than the middle-european armies. Why? Less people to spread disease, less diseases in general
I'm not sure about that. Cold weather is a great protection against diseases, and the Scandinavian cleaness culture certainly helped even more. But exposure to different kinds of diseases is good in the long run. The middle-European familiarity to deadly diseases created a people with strong immunity. Let's remember that ~80% of the native American population was anihilated by European diseases for which the conquerors were already immune. And if that happened in such a large scale, we can infer that it also happened in a smaller scale, e.g. of continental Europeans attacking island folks who, without such genetic protection, may have fallen easier than they should.
My point is that there are many factors that contribute to a given culture's military success, and one's variety of antibodies is also one of them.
As a side note: I don't believe Scandinavians were not exposed to diseases. They were seamen, and there are settlements and genetic markings found in Ireland, Southern Italy, the Black Sea and America. Just imagine how many different bacteria and viruses they got in contact! And some of them sailed back to Scandinavia, bringing with them these microorganism. Therefore: Nordics did experience a lot of diseases.