Resistance museums CPH vs Oslo

We did not get to the museum while in Copenhagen so I can't speak to that one but we did visit the one in Oslo. It was very impactful and I think is an important museum to visit. My whole family left the museum just amazed at how much we learned, and how much we never knew about this period in history in Norway. As someone of Norwegian heritage who had family living in Oslo during this time I found the museum moving.

The museum in Copennagen is located near Amalienborg Palace and DesignMuseum Denmark. Perhaps you and your wife could split up for a couple of hours.

My visit to the Copenhagen one was many years ago, and I think it's been totally redone, so can't comment on it now. The Oslo one is good. As well as the exhibits, it is in a historic castle with a nice view over Oslo. One thing to consider is that, all things equal, Norway has more resistance history than Denmark -- not because Danes were less patriotic, but because living in a small flat country that fell to the Nazis in a matter of hours, there was simply less ability to resist. And that was the case throughout the war. There were a few important events in Denmark, especially the rescue of the Jews, but a Norwegian resistance museum has a lot more to work with: months of very heavy fighting in 1940, more fighting in northern Norway in 1944, the British Lofoten commando raid, the "Shetland bus" boat missions, the attacks on the "heavy water" plant to try to stymie any German nuclear development, fighters dropped by parachute in the mountains, etc. But your decision may well depend (and quite reasonably) on the fact that there is a lot else to see in Oslo and your time there is much more limited than Copenhagen.