Reminds me of Turtles 3 where they travel back in time to 1602 AD Japan and there was a European white man there with a gun and a canon. So, he was trading with the emperor or something like that. There were the Samurai who may have been more deadlier than the Vikings. But of course they were both pirates like you said. I wonder how the two groups would match.
Vikings vs Samurai
If the Vikings fought the Samurai, who would win? If the Japanese were more ninja, more healthy, athletic, faster, more skillful with a sword, then they would probably win. Vikings may have been stronger but the Japanese may have been quicker, smaller, more flexible. So, if they were fighting in a jungle, the Japanese would probably win.
Samurai vs Gladiators
Well, I might compare the Samurai with Roman Gladiators who were possibly more deadlier than the Samurai on average.