I agree. Fjords in Norway are very beautiful, but a couple of Fjords is likely enough, if you are on a cruise. The coastal cities like Bergen are very interesting in there own right for different reasons.
I think your situation comes down to if you want to do 2 countries with one trip and and thus have fewer stops at each, or you want to just concentrate on one country. I really enjoyed our Norway only cruise . Also enjoyed our Iceland / Ireland cruise a couple years later. I would give Norway the edge, however.