My husband, our 3yr old and I are planning to fly one way between Oslo and Bergen and ride the Bergen railway train the other way. We don't have enough time (and my 3yr old will probably not have the patience) for a Norway in a Nutshell tour between these towns, so a combination of flying one way and taking the 7hr train ride the other way seems to be our best option. Given this, I would love to hear if you would recommend riding the train from Oslo to Bergen over Bergen to Oslo or the other way around or if it doesn't matter at all. Please advise.
Bergen Railroad E to W and W to E cover the same ground, just in an opposite direction. If you miss/skip the NiN route you miss the Flam Line railroad, one of the steepest non-cog rail lines and spectacular scenery. (The Bergen Line is a E-W section of Norway, the Flam Line is a vertical section from the Hardangervidda (high plateau) to sea level). You also miss the fjord cruise.
Given your ability to move around on the train and boat, your 3 yo isn't restricted as in an air flight and can move around.
I would suggest doing tho Oslo-Flam-Bergen as a one, or better yet two day journey E to W, then return to Oslo by air after a one or two night stay in Bergen if you have the time.
Do make reservations once you have decided on your travel plans. There are a few rail stops between the two endpoints - ideally, you would like to have the same seating assignment for the entire journey.
As Edgar suggests, you can still do the NiN over 2 days with an overnight stop at Flam.
Depart Oslo by 8:25 train. By mid - afternoon you are in Flam; take a breather & stay there.
Next day complete the NiN till Bergen. You will have plenty of time to decompress.
You can take the flight back to Oslo day after that.
We took the train from Bergen to Oslo. It was a very nice, scenic ride. I walked through the train on my way to the snack bar and noticed that there was also a "family car" and a little room where the kids could watch TV (maybe it was a video) to keep them occupied. Hope you enjoy the trip!
I agree with Edgar - if you only take the train between Olso and Bergen without the rest of the Norway in a Nutshell parts (Flåmsbana, boat on the fjord, bus up from the fjord), you miss the most scenic parts. I was disappointed in what I saw on the train ride from Oslo to Myrdal; I didn't find it as scenic as Rick promised.
So, even with a day, I'd do the NiaN one way, and fly the other way.