We are planning to do the NIN tour from Oslo to Bergen. We will stay in Bergen for a few days before we had back to Oslo. Is the fastest route to fly back so we can save on time? Or is a high speed train and ok thing to do knowing we’d lose a half day of sightseeing in either Bergen or Oslo due to our time constraints.
You'll save about 2-2.5 hours taking the plane over the train.
Don't forget you have to add in travel to and from the airports as well as a two hour check in for security, etc.
Yes I was curious if we really save time or if a fast train back it still better if we did it early enough.
The train between Bergen and Oslo is sightseeing at it's best. It's lovely! I don't know what the NIN tour is, but I took the train one direction and flew the other. It was very interesting to fly over the mountains, but also beautiful to ride through them in the train.
The NIN route covers most of the mainline train route from Bergen to Oslo, so you won't miss out on very many miles of scenery by flying. It looks like much less than 50 miles (probably under 40 miles) between Myrdal and Voss, the part NIN skips by dipping down to the fjord.
I always prefer trains to planes, but that's because I'm retired. The good thing about the Bergen to Oslo flight is that you needn't pay a lot for transportation to and from the airports as long as you don't fly out of Bergen so early that you can't use the Bybanen light rail system. (That's probably not the fastest way to get to the airport, though.)
You'll save a bit of time by flying, but not that much. On the other hand, the train offers great views. It will allow you to see the views between Voss and Myrdal. But also, it will allow you to see the views from both sides of the train.