Please help! Swiss franc or Euro?

You will need Swiss franks. You will get them at ATM, in Europe called bankomat.

You probably can use your credit card most of the time. However, you will need local currency for smaller purchases.

Before using a credit card, check if there is a conversion fee. (I have 2 credit cards, one has no conversion fee, one has a 5% conversion fee) The conversion fee is applied to whatever amount you put on the card, so for every $100, I would be charged $5 on the 5% card. Obviously I use my other credit card when I travel internationally.

My first choice is to use my debit card to take out cash from an ATM (bankomat). My debit card has no conversion fee but many do. Check that before you go as well. TIP Use ATM's owned by local banks and that are preferably on the bank site (either in it or attached right outside). There are ATMS owned by Travelex and others where you get poor conversion rates and higher fees. I have never been charged a fee using a bank ATM and always get whatever the bank conversion rates are at that time.

The worst thing I could do would be to take a cash advance on my Credit card. Not only are their fees involved, but I am charge interest from the moment I take the money out of the ATM.

What I do:

I use my debit card to get cash from a local ATM (Please see below about Dynamic currency conversion). When I am only in a country for a few days, I take a smaller amount and use my credit card for larger purchases. Be advised that there are still many small businesses that will only take cash and check with restaurants and B&B's before assuming you can use your credit card. Because my debit has no fees attached, I can always run to a an ATM and get more if needed.

Use my no conversion fee credit card for larger purchases. On a side note, read about the Currency Conversion fees here:

https://thepointsguy.com/2015/06/dynamic-currency-conversion/

I always push the button that says I want my money processed in the local currency. Avoid anything that has it in US dollars.

The hard part of using cash is that it becomes useless once you leave the country. (Too expensive to change back small amounts!) We have had good luck paying some bills part cash and part CC. For example, when we left Munich in 2018, we payed part of our htoel bill with our remaining euros and put the rest on the CC. Our B&B in Switzerland would not take a Credit Card, so we set aside the cash we needed and used the rest to get drinks at a hotel where we were enjoying the live music they provided. We have even stopped at a few convenience stores and used up our last bit of local currency on snacks. And once, I brought home 10 British candy bars purchased at the airport with the last of my pounds. (Made great small gifts to friends). It kind of becomes a game to get rid of it all (and the game of trying to estimate how much we need).

What I NEVER do:

Exchange money here at home before going on a trip. I truly don't understand why people do this. They pay extra fees for money that I can walk off a plane and get at the airport (although I do have to look harder for bank ATMs at the airport)

Exchange money had a "money exchange store". Why would I accept their rates and fees when my bank at home gives me a better rate without any fees.

As for using Euros in Switzerland, I only tried it once and they were refused. (it was right at the border, I had used all my SF and needed an Austrian Vignette. I asked if I could pay in Euros...not allowed, However, this small convenience gas station did take my credit card so it was fine)

I guess it's possible that there are places in Switzerland that will accept euros, but I can't recall any and I wouldn't count on it. You will need Swiss franks (CHF).

If you're only there a short time, the easiest thing to do is just use credit cards as much as possible. You may need some cash for certain situations, so take out a small amount from an ATM. Other methods cost more (sometimes much more.

Connie's ideas of how to get rid of franks as you are leaving Switzerland are good.

Whether you are using your credit card or using an ATM to get cash, ALWAYS be watching for dynamic currency conversion, and always refuse it. It can be phrased in sneaky ways, such as "would you like to lock in an exchange rate of $XXX.xx?" Any time you see dollars, run - always make sure your transaction is processed in CHF. In 2014, I only had a few transactions that wanted to use DCC; in 2017, almost all of them did.

....I can walk off a plane and get at the airport (although I do have to look harder for bank ATMs at the airport)..... I don't understand why anyone would want to do that especially if the sole ATM is out-of-order or out of cash. Then just have to find another one.

My husband and I were in Lauterbrunnen last September and used Euros and a credit card until we made it to an ATM for francs. We were on the RS My Way Alpine Europe tour and the tour manager advised us that many places take Euros with no problem. You even get your change in francs.

My choices would be a combination of pay with credit card and find a local ATM.

There are certainly places in non-euroland that accept euros, but 1) You can't count on it; and 2) You will certainly get a very poor conversion rate. It's something I've always avoided, but I acknowledge that if you're doing something like a one-day stop on a river cruise in (for example) Budapest and can put almost all your expenses on a credit card, paying for a cheap souvenir with a 5-euro note may be a reasonable move, even if there's a 1.50-euro profit to the storekeeper. You probably can't get less than 20 Swiss francs out of an ATM; for all I know the minimum may be even higher.

For longer visits, you're going to be wasting money on all your cash purchases until you find an ATM.

Yes, you will need Swiss Franks. Some shops and restaurants in tourist or border areas will accept Euros (notes only, no coins), but at an inferior exchange rate. Sometimes 1:1, so you would be losing (currently ~14%). Change given in Swiss Franks.
SBB ticket machines and ticket desks accept Euros at the current day rate.

Best place to get Franks - Bank Cash machine (ATM) once you arrive in Switzerland.

You can exchange at larger stations, but exchanging cash will be at a worse rate than an ATM.
Or use a credit card. But always check first. Some smaller places do not accept cards or have a minimum amount for card transactions.

Edit:
Watch out for DCC on either credit card or ATM transactions. If you don't know what that is, look it up.

You probably can't get less than 20 Swiss francs out of an ATM; for all I know the minimum may be even higher.

I have never seen less than CHF 20 in an ATM, often it is CHF 50 + 100 + 200.
Multiples of CHF 100 is the default payout. Some tourists think they will have trouble changing them. Not an issue, everybody pays with them.

Take out a credit card in advance that offers no foreign transaction fees. Capital One offers this, not sure what other companies do.

Another option is to use Apple or Android Pay. Then if you want some cash, use your ATM card there. My last few trips have literally been all using my iPhone Debit card and spare cash. I like using the iPhone because at a restaurant, when I pay, they bring over the machine and I tap my phone on it, and they walk away.

Yes to Credit Cards with no FX fees. I use the Capital One Quicksivler Cash Reward with no annual or FX transaction fee. Even better, the Quicksilver card has a 1.5% cash back on every purcase resulting in a negative fee. Capital One does not require foreign travel notifiaction.

Our experience in Switzerland two years ago was that credit cards, including American chip and signature cards were not a problem in staffed locations. I did not use my Capital One Visa for automated transactions (i.e. train ticket macines).

Of course your experience may be different, but the only place we encountered in three days in Switzerland last year that did not take credit cards was the Chinese restaurant in Murren. And they took US dollars, Swiss francs, or Euros. I would use your credit card and would only take out money if you have to.

The only place that did not accept a card payment during our trip to Switzerland was an Italian resturant in Tirano at the end of our Bernina Express excursion, but that was Italy, not Switzerland. The Italian resturant did accept Swiss Franc if you didn't have Euros.