I'm not unionized (I cannot because none of them are purely work focused here and I deeply disagree with their other views), but here is an observation from Norway, 20 years ago:

AFAIK, unionized companies in Norway statistically were more profitable than ununionized ones.

This might of course be because it is more tempting to unionize when there is a lot of money to be had, but I remember one extra detail:

In between (friendly) ribbing I also remember the union people here being focused on working efficient so that our bonus would increase :-)