Samsung Pay just picked up support from Chase Bank, one of the more important banks the service needs in its push to work with all debit cards. Samsung Pay's differentiating feature is MST, which allows supported phones to send payment information to magnetic swipe terminals without the need for NFC — though it works with that, too.
So, in theory, Samsung Pay has a leg up on both Apple Pay and Android Pay, since it lets users pay with their phone even if the store hasn't upgraded its terminals or made whatever deals are necessary to work with those services. But that leg up requires that your cards actually work with the service. Credit cards from Visa, Master Card, and American Express are all supported, but getting debit cards to work requires Samsung to go bank by bank. Samsung says that Bank of America, Citi, and U.S. Bank are all on board — and now Chase is, too.
Samsung Pay isn't universal, yet
Even if Samsung gets 100 percent of banks to support its service, you still can't be 100 percent sure that you will be able to leave your old plastic cards at home. MST is great, but in our testing we found terminals weren't always reliable in receiving its signal — and some terminals (like gas station pumps) may never work with the technology. It still gives you much broader coverage than NFC-based payment systems, but it's far from universal. So it's still a crapshoot, just a crapshoot with slightly better odds.
Samsung Pay also only works with a Samsung's latest phones — the Galaxy S6, Galaxy S6 Edge, Galaxy Note 5, and Galaxy S6 Edge+. But even with all those limitations, Samsung's service is slowly building toward a level where you can actually trust that it'll work when you tap. Verizon has deigned to allow it on its network, and Samsung has previously said that support for Discover and for gift cards is coming in the future.