i hope im not bothering people, but it depends on weapons, armor, mobility, range, and numbers, the samurias have armor EVERYWHERE, vikings too, mobility would be similar, vikings would use bows, samurias would have long bows, crossbows, or something else, and numbers: i would assume samurias would be in 5s or 4s, and vikings would be in huge amounts. weapons, well vikings would use broad swords, axes, or bows,and sheilds, samurais would use katanas, long bows, sheilds, and stuff. so, it depends on all the above.
your right mate, and it could end depending on one tiny mistake. spot one.