This a matter of opinion ,in retrospect I think the Romans were better because they were more advanced and were extremely intelligent.They had many strategy’s while the Vikings were more of a “Kill now, solve later” type of people.In a standoff between the 2 ,I reckon the Romans would win,in many battle they were outnumbered but still won by sticking together.In a battle again Boudicca and here 100,000 troops versus The Romans 10,000 the Romans won.