Samsung has been slowly but steadily adding new markets to Samsung Pay, which is now supported in more than a dozen countries. That includes a few new ones today. Residents of Sweden (previously in beta) and the UAE can start making payments today. There's also early access (i.e. a beta) for Samsung Pay in Hong Kong and Switzerland.
You need a recent Samsung device to use Samsung Pay, whereas Android Pay works on anything with NFC. That's not just an arbitrary block, though. Samsung Pay works at NFC payment terminals, but it also uses MST hardware for contactless payments on almost anything that can read a credit card. Samsung phones have that and others don't.
Like Android Pay, Samsung Pay needs support for your bank. Samsung's announcement didn't indicate which specific banks were included, but it did note that pre-paid cards are compatible with Samsung Pay in Switzerland. In addition, Samsung Pay on the Gear S3 smartwatch will begin working in Russia, Sweden, and the UAE in the coming days.