I think this has some relevance to the discussion:
Three different events depicted in the Bayeux Tapestry (11th century, Norman conquest of Britain) showing Norman longboats with shields on the sides of the boats :
The boats without shields appear to be the ones either transporting horses or general stores.
Explore The Bayeux Tapestry Online
Who were the ...
Yes, archaeological evidence strongly suggest that at least some warships did but, considering the vast numbers of ships that were built during the Viking age - and in many different locations - we cannot assume that all Viking Longboats had shields along the side as only a small percentage have been recovered. Further, it's hard to know in what situations ...
Since you are asking for "arguments from both sides" I give you my arguments,
without references, except some pictures of somewhat later period.
It is unlikely that the shields were hanging outside as shown in many
modern pictures, when traveling:
A shield is a precious piece of equipment, if hanged overboard, it can be lost, and more importantly ...