Where is your trip to? 36 hours isn't a very long time, so my answer would probably differ depending on your main destination.
I am in the same quandry. I will be in Copenhagen for five days and will have about three days to travel somewhere else in the area.
Just what I was told by someone who travels a lot. I think he was particularly taken by the fjords.
Stockholm it is. Thanks
Well, the most dramatic and impressive fjords are found outside of Bergen, so if that's what you want I suggest you skip both Stockholm and Oslo and go to Bergen instead. The Oslo fjord as seen from the city is just a wide expanse of water surrounded by relatively flat land... which in that respect makes it very similar to Stockholm, where there's plenty of waterfront running through the city. You will find, though, that Norwegian prices make Sweden seem like a very good bargain indeed. I suggest reading some travel reports on the internet, since a lot of e.g. North Americans tend to visit both places on tours and may offer a comparison that won't be tainted by the potential bias of locals :-D.
Our problem is not 36 hours, but after 10 days in Sweden on pilgrimage, we will have about 1 week... and wonder if train to Oslo to visit a friend there is unreasonable use of time. One of us is Swedish descent, the other Norsk. The swede wants to look into ancestral roots, but doesn't want to miss the friend in Oslo, but doesn't want to spend the entire week on the train.... is the trip between the two cities worthwhile? I know Bergen-Oslo is worthwhile! Is there something else in Sweden that would be worth much more since time is limited? Visby was suggested...
I have lived in both and live just outside Stockholm today. Depends on what you are looking for really?