Most Viking strerotypes were promulgated by the English their enemies. Sort of like if we asked around in the Middle East today for an accurate description of Americans. Vikings were technologically more advanced than mainland Europeans. That's how they dominated them in war and yes even "culture". English women appreciated that Viking men used combs and bathed often something it took awhile for the Englishmen to figure out.
Man for man, a Viking military force was no more effective in actual battle than the European warrior bands of the day. The Vikings' military advantage was mobility and surprise, due to the longship and the fact that they were (at least initially) raiders who could pick their targets. Their poorly organized victims were unable to provide adequate point defense against an enemy who could strike anywhere while drifting away from serious resistance.
The Vikings' great weakness was their own political fragmentation. On the few occasions when a Viking king was able to put together a broad enough pirate alliance, Viking invasion forces were certainly capable of going toe-to-toe with serious European armies (as opposed to local levies called out to oppose raids), but their success was quite mixed.