Money is a complex topic in Cuba. If you are travelling to Cuba, taking enough Swiss francs or euros in cash with you is a good idea. You can then change the money into the Cuban tourist currency CUC (peso convertible) at a bank or bureau de change (CADECA). The CUC is pegged to the US dollar 1/1, so approximately 1 Swiss franc per CUC.
But the queues at money changers are long, and they occasionally run out of money. Many hotels let you buy CUC as well, but some add a markup. It isn’t possible to exchange money at casas particulares – the popular private boarding houses.
As far as I know, the 10% tax applicable when you change US dollars into CUC is still in place. But this tax doesn’t apply to other currencies like euros and Swiss francs. The Federal Department of Foreign Affairs (FDFA), US dollars can only be exchanged in Cuba at a high cost.
When you use a payment card to pay, transactions are always converted between CUC and US dollars. That means the 10% tax applies, and you may pay additional fees specific to CUC/USD exchanges. Because of that, using credit cards and debit cards in Cuba is generally not recommended. Another problem is that some payment cards may not work due to US sanctions on Cuba. If you want to use cards, consider taking multiple cards in case one or the other doesn’t work.
It isn’t possible to say which card would be the cheapest across the board. It all depends on how you use it. The PostFinance debit card could be the cheapest if you hold at least 25,000 francs at PostFinance. If you meet that requirement, you can make unlimited cash withdrawals worldwide without paying withdrawal fees. However, according to the FDFA, the PostFinance card cannot be used to make cash withdrawals or to pay at POS terminals in Cuba. PostFinance itself doesn’t publish any information about the use of its debit card in Cuba.
Foreign payment cards: Revolut and TransferWise are both cheap options for international withdrawals and payments. But Transferwise clearly states that its cards do not work in Cuba. According to posts in online forums, Revolut users claim to have successfully used their Revolut cards for cash withdrawals in Cuba.
I hope this helps.