Is it a good idea to buy tickets ahead of time for intercity travel in Switzerland or between Bern and Paris ( using RailEurope )? Also, is there a difference between Jungfrau Railways and the Berner Oberland Pass? Thanks.
Personally I think RailEurope should always be avoided. It is a travel agency to sell tickets to N Americans. Prices generally include heavy mark-up, limited trains, and no discounts, We normally buy tickets as we go for convenience and flexibility. However, many train systems are now offering discounts for advance purchase so there is some price advantage. You best price will come directly from the train site.
If you book your Bern-Paris ticket well in advance (up to three months allowed) on the Swiss Rail site, you can get a discount fare as low as 41 CHF. The standard 2nd class fare is 124 CHF so it pays to book ASAP. Note: This is for a direct Bern-Paris TGV. If you pick a departure time that requires a connection in Basel, the fare will be different.
For information on passes and cards for Switzerland alone, go here.