Arch., I did expect better of you - Viking is the old norse word for raider, yes... but the Danes and Norwegians did also fight concerted military campaigns, from Alfred the Great's time right up to the Norman Conquest. Huiscarls and Thegns were basically full-time warriors. The Nordic and Saxon troops chose mail and leather armour. Did they have the option of plate? One has to assume that they knew of it, at least.
So far as I know, there was no culture of plate armour, in any form, in the British Isles or Scandinavian countries after the Romans left. Maybe it was a technique that smiths just never learned? Then again, they managed to make plate helmets, not just mail coifs.....
I'd like to suggest in addition, that mail has one HUGE advantage over plate.
You can stuff it in a sack and carry it around. Plate is bulky and awkward when one is not wearing it. Mail can be rolled up like a blanket. Perfect for armies that march long distances in bad weather and hard terrain, and really easy to pull on in a hurry. In a pinch, you can sleep or swim in mail too.