Jan 31, 2015 - 6:23 PM
Welcome to MySwissAlps, debflint!
A Swiss Half Fare Card gets you a 50% discount on all trains and many cable cars/gondolas. If you download the map you can see all the details. A Regional-Pass Bernese Oberland gets you free traveling in the entire region (starting in Bern) by train and many cable cars too. Again, the map will show you what's covered. There is a 10-day version of this regional pass, so this could be a good alternative to the Swiss Half Fare Card. And more convenient as you can just start traveling without buying tickets very day.
Regardless of which one you choose, you can get the pass at a lower price if you buy before February 2. See this and this topic for details please. All prices are listed in the Price section of the pass pages, like here.
Apart from the pass you need a return ticket from London to the Swiss town where you can start using your pass. This post is worth reading I think.
Did this help you decide?