Spartans bro. And it isn't close.
Nice Hollywood movie. Let me hit you with some facts.
1. The Spartans were notorious for being homosexuals
2. The 300 fought an army of slaves
3. They were classically Mediterranean sized. Compared to the hulking Germanic nords, pipsqueaks. Roman historians would often revel in the stature and supremacy of the Germanic.
4. They were only really known for their tactical strategies as a unit. Really they stole this from earlier Greeks.
5. They wore speedos and used BRONZE AGE weapons. Nothing compared to the iron supremacy of the nords.
6. The Vikings used all the strategies of the Spartans. These were not unique formations, like the Phalanx. They may have been some of the first to utilize it, but everyone since then used it... Including the Vikings.
7. Vikings used hallucinogens and psycho-tropics, ale, and special herbs, to numb pain and go into a frenzied rage. These were known as Beserkers.
8. Both The Vikings and The Spartans had a distinct warrior culture. But the Viking one was much more extreme. Dying in battle was seen as the utmost honor, and thus was rewarded with afterlife in Valhalla (Heaven)... Whereas a life without glorious battle and death, was seen as weak, pathetic and a one way trip to Helheim (Self explanatory).
9. The Spartans were defenders, whereas the Vikings were raiders and conquerors. Vikings had the experience of actual variable combat scenarios, while The Spartans stayed in their barracks, training. They never encountered the various scenarios that the Vikings did.
Vikings as warriors are superior.