Thoughts on HappyRail.com website

Never heard of it.
What is SDP? Saver Day Pass? When I look at this site, it quotes 64 EUR, does not say what day it is for, and and asterisk says "* You need to be in possession of a Swiss Half Fare Card"

The Saver Day Pass is offered by SBB at their site and not requiring a Half Fare Card.
https://www.sbb.ch/en/travelcards-and-tickets/tickets-for-switzerland/1-day-travelpass/saver-day-pass.html

You buy it ahead and the cost increases as you approach you date of travel. Maximum of 60 days in advance for the lowest price, 52 CHF.

I see from your other post that you are going to Wengen on July 28, and leaving on July 31. July 28 is a Sunday and the Saver Day Pass is 70 CHF for that day. You can still get the SDP for 52 CHF for July 31. But do you intend to pay full fare for the other trips you have planned while you are in Wengen? You mentioned going to Grindelwald in your other post.

I have just used the SBB site and not had difficulties. I would encourage you to purchase from the Swiss Railway itself.

Further info, for July 31, you could get 2 Supersaver tickets which require you to travel on a train specific itinerary for 68.80 CHF rather than the 104 CHF with 2 Saver Day Passes.
You would not want to do Supersaver tickets for July 28 since you cannot be guaranteed when your plane will arrive or how long before you get through immigration and get your luggage.

Why?
Another "me too" reseller site trying to hook foreigners who do a quick internet search and go to the one that comes top in the search.
There is no way then can undercut SBB, that is the "correct" price. All tickets are ultimately issued by SBB.

Saver Day Passes start "from as little as CHF 29 with a Half Fare travelcard, and from CHF 52 without a Half Fare travelcard" . See here: https://www.sbb.ch/en/travelcards-and-tickets/tickets-for-switzerland/1-day-travelpass/saver-day-pass.html
Note the "from" in those prices, they go up nearer the date, on some dates they cost more.
Zürich Flughafen (airport) to Wengen costs CHF 88.40
Wengen to Basel costs CHF 75.40

I would just buy your Saver Day Pass from the SBB website as early as possible, simpler.

Thanks to all that replied to my inquiry about Happy Rail.com. I have spent 2 days researching and cost comparison and for my time and train journeys in Switzerland. The SDP (Savor Day Pass) was the best way to go. I did a comparison as suggested with SBB site and did find them cheaper for my short leg from Wengen to Basel. However, Happy Rail beat SBB when it came to my long leg from Zurich to Wengen--- over $50. The key is--- you have to get on board with the SDPasses (60 days ahead) as soon as you can. I could have saved more if I had known about them 60 days ago instead of 30. I focused only on the Swiss Rail Pass in my earlier searches. Again, thanks.

Actually Saver Day Passes are higher on Saturday and Sunday, even when you go out the full 60 days.

Did you note that your Happy Rail says you need Half Fare Card for their offer? That is 120 CHF per person in addition. Without it, the Saver Day Pass they are offering will be invalid and you will get fined if you try using it.

Seriously, nobody can undersell SBB, since they are the exclusive seller of tickets for the trains they operate.

My thoughts- the happy rail site is much easier to use to find the super saver fares from point to point. I spent a couple of hours yesterday researching fares, and the sbb site made you click on each time separately to see what the save fare would be. Happy Rail shows all the prices in one screen and lets you choose with or without the half fare card.

op: if you already had your mind made then why come here and ask for advice? Nobody beats SBB prices - and you’ll find that out when you board your train with wrong tickets from happyrail.

I've also never heard of "Happy Rail", but if they've delivered your tickets I suppose that's all that counts. The most reliable agency to use for tickets in Switzerland is SBB, as they actually operate the rail network. I can't imagine that a reseller could offer cheaper tickets than SBB.

Some research on Happyrail.com.
1. It is an on-line reseller of European train tickets located in Leiden, Netherlands. It is a division of the rail tour operator Treinreiswinkel. They been in business for a while.
2. They appear to be very reliable.
3. Since March, 2019, they have been able to offer Saver Day Passes and Supersaver SBB tickets. These are transmitted via e-mail in pdf form after the purchase is made.
4. As another poster pointed out, their site quickly identifies the cheapest available option for tickets for any given routing on a given day. If the lowest price option is a Saver Day Pass, they offer that. If it is a Supersaver ticket, they offer that. The price is the same as SBB, quoted in Euros. You have to click on the "conditions" button to see what you are actually getting for the quoted price. Supersaver tickets are train-specific, only valid on the specified routing. Saver Day Passes on the date specified.
5. They add 1% for Visa or Mastercard payment, just like Trainline.
6. They may be easier to deal with for credit card payments than SBB, which requires 3-D security for credit card payments.

So their chief advantage is ease of use to identify lowest cost Swiss train tickets. You could use them for research, then buy those tickets directly from SBB if you wanted. Also, the credit card vetting issues are easier.