Which Rail Pass?

If that is all you are doing, just buy point to point, but I suspect you will also be doing some of the mountain railways and lifts, in which case a 120 euro Half Fare Card would save some money. Are you 25 or under? Swiss Passes are less if you are, but they are still quite pricey and only give a 25% or 50% on mountain railways like the Jungfraujochbah, Schilthornbahn, or Gornergratbahn.

The regular, 2nd class fare for those three routes adds up to $220, but you will have other expenses. For $268, the Swiss Travel Pass version for 4 consecutive days allows you to hop on lower-level trains (e.g., as far as Muerren or Wengen, not just Interlaken), buses, boats, and some museums, plus offers the 25-50% discount on higher lifts. If your trip fits into a 4-day period, that pass would be my choice. If you will travel from Zermatt to the Italian border on the 5th day, then that's about a $60 value to buy separately.

There's also a pass for 3 travel days spread over a month, but then you get less lower-level coverage on the in-between days (value hard to estimate without more info).

The Half-Fare Card is better than no pass, and a smaller up-front investment. You'll show the card to buy each transport ticket within Switzerland for half price; when purchasing online or from a machine, there's a button for that.

Thank you Sam and Laura for the quick reply! We are not 25 and under. But we do plan on doing the mountain railway in the Jungfrau. So it sounds like it will be bast to do the half-fare card and then buy each leg of the trip individually?

Thanks again for your help!