What is the difference between 1st class and 2nd class tickets on the Golden Pass Rail panoramic cars between Lucerne and Interlaken and Zweisimmen and Montreux?
The differences are the same as on any other train. 1st class gives you more room, fewer seats.
I went in several first class cars while in Switzerland just to "take a peek" and I really could not tell much difference. Swiss trains are great, 2nd class was super clean and worked well for us. I only rode the Golden Pass between Lucerne and Interlaken (not the true panoramic train, just the regular train) and the views were great, no reservation needed, plenty of seats.