Best direction between Oslo and Bergen
 

Which is the direction to travel between these two cities for the views from the train in early September?

Doesn't really matter at that time of year - there is still sufficient daylight. However the section between Geilo and Oslo is not particularly interesting and as it's a long day I would choose Bergen - Oslo direction then you can safely snooze from Geilo to Oslo without fear of missing anything. Seen plenty of jetlagged tourists nodding off on the interesting bits!