Originally Posted by Lost_Luggage_in_SEA

Just my experiences: YMMV.

In recent trips to the UK, I've several times had my visa card rejected by a contactless reader on a bus but had the same reader accept my mc (both issued in the USA). I've no reason to think mc is more reliable than visa: in my case visa is always my first choice so it has more opportunities to fail. It's not related to a problem with the visa card itself but occasionally, some contactless readers reject it for no apparent reason. I suspect that many credit cards issued outside the country you are travelling in can occasionally fail for unknown reasons but another card will work for equally unknown reasons (unknown that is, to the owner of the card and to the bank that issued the card). As a result, I always try to carry different kinds of cards including at least one visa and one mc.

There are still many places that won't take credit cards. Some are not surprising (eg. mountain restaurants in Switzerland) but some smaller café places in cities are cash only and I've found places I would expect to accept credit cards that don't (eg some funiculars in Switzerland). Unfortunately, there isn't always a sign that says "cash only" or the equivalent in the local language.

I recommend using contactless wherever possible. Using contactless makes travel on some public transport systems such as London much easier and quicker and the automated checkouts in grocery stores are also faster with contactless. There are now WCs/restrooms that require contactless credit/debit cards to use them (eg. Dartmouth in the UK).