and my money goes to....
Samurai
why.... Because I'am biased
well, after reading about all some very knowledgeable pleople have posted in this thread, it is quite evident that the knight has serious things going for his gear, also, for the kind of diversity the european knights went trough in their wars, thier discipline it's supoused to be also very strong.
I must state first of all that I'am VERY IGNORANT, yes with capital letters, all my serious knowledge for this topic comes from videogames, anime and in the best case from discovery channel or something like that and maybe some books. So my opinion is not to be taken as nothing more than the opinion of a very narrow and ignorant modern mind.
Mr katumoto stated a good point, that in my narrow view of the world gives the samurai the advantage, and that is the state of mind.
As for the little historical knowledge I got, Dr. Isaac Asimov's divulgation essays describe thier origins and ways as something very far from noble, the Chevaliers beign some sort of very priviliged and rich war boy which was feared because of it's affection to pick up on unarmed and poorly equiped peasants. Their wealth and equipment puts them in a favorable position of dominating lands and masses of peasants (also beign the great source of income they used to be then...) came to be very appreciated by kings and noble classes, which in return of favors granted more money, authority and perhaps the public approval that led to the romantic development of the image we commonly have today of them. After that kingdoms and nations comming in conflict with each other put their knights at the point of their armies which might have led to the military evolution we are aware of.
With the "public" aproval of the kings, and therefore of pope, comes the divine side of the knight's task, keeping the lands safe from foreigners, and maybe recover the holy land. By then the knights are showered with power, wealth, fame, and an aura of saivors. They as a social class eventually got betrayed and disposed of by political means. Very nasty indeed.
From all this, the little historical perception I get of the knight culture is that their code of honor was forged more by public relations than by a way of life, during their existense they might have found the need to hone their skills, after all war was their business, and skill is a very important building brick in the pursuit of victories. But their motivations and sense of their own place in life seems not to be so romantic at most times during their existence.
Their training may have been very hard, and they had to be skilled but then comes the samurai.
My ignorance about samurai I think is bigger than that of european knights, but as little as I know of them the little historical stuff that has reached up to me gives me the perception that samurai had a bigger thing going for their view of life and war, and art for that matter than the european knights had for their equipment and motivations. I have only read the five ring book, and beyond beign for some people a demi adaptation of the chinese art of war, describes many points in the samurai culture that I think a knight of the time would have had trouble dealing with. As someone already said, a samurai would go to war with one and only one thing in mind, a void, no fears, no remorse, and the total dedication at one goal, kill, not kill or be killed, not try kill the most, nor getting fame and glory, just do what you rtrained for and what you were born to do, honor the tradition and let the battle engulf you. If you die, you are happy with it, if you don't, you just accomplished what you came to do and live for.
From Miyamoto's view of things there are no doubts, nor strange motivations, just killing.
there is always a but, Miyamoto's book accounts that his own style and viewpoint of the combat were not common in his time, that means that in his time most of the japanese warriors did not follow his ways, I don't know how much time Samurai class outlived Miyamoto's work, but if it was enough to be wellspread among the samurai class in Japan, they had a very good tool in their philosophy which in my little experience of life gives you an edge at whaterver you do, it does not guarantee material success, but pretty much favors it, and also guarantees spiritual success in your mind.
and that's why Samurai would have my simpathy and my money on a bet.
It's of course pointless to argue seriously about who would win, no way to proof, I do not think modern praticioners have the same level both kind of warriors had on their splendor days, be it higher or lower, it's just not the same probably.
As for Mongols (or huns?), I was made to believe (by some documentray or something like that) that they in fact kicked Europe's derriere, made it as far as Hungary, and that they just couldn't be stopped at the time, also heard that some troops of the Mongols set foot in Italy itself,and that the Pope (not as a benevolent figure as we have now) had to pay a good contribution to the mongols to ensure the survival of his towns.
Then mongols went back because of the death of the Khan, and the empire decayed, maybe because of fragmentation, and mostly because of the sick size of it's territories was something difficult to mantain.
As for spanish conquest I'am a bit more informed:
Yes disease and deceit won the wars for spanish conquerors in America, their firsts direct battles with the Aztec empire despite of attacking on surprise against the Aztecs, the spanish troops got their ass seriously kicked (I don't have to go about the spanish having on their side, surpise and treason, horses, steel, ARMOR, and even fire arms) after all, Aztecs had comparatively poor crafted bows, and their weapons were made of wood and stone, but had some serious way of viewing war as a way of life, a force of nature and also were well used to eat the heart of their enemies, as a way to honor them, after some serious retreat, Hernan Cortes made pacts with other enemy tribes of the Aztecs in the region and with their help and the problems that the new diseases brought, put an end to the aztec domination. Later on reinforcements came to america and the rest is history.
So as fictional as the match goes, I put all the odds on those that seem (to me) had the greatest sense of dedication known to human warriors,
the Samurai.
P.S. sorry for the first big post and the lousy english.