Ditto....I've had 14 of them over the last 7 years....2nd is just fine except for rush hour times and even then if you board the train right when it arrives, you'll have no trouble getting a good seat and room for luggage. As for going to Wengen, you are covered by the pass Interlachen to Lauterbrunnen. From there to Wengen is only one short hop on the next train going up to Kleine Shiddigg(5 minutes)... and on all mountain trains you will get a discount.

TrainLover