Also note that the tourist cards aren't good value unless you plan to make very heavy use of the MTR (and no use of buses, trams etc).

In nearly all cases it makes more sense just to get a normal on-loan Octopus card.

You now also have the option to pay for the MTR and buses (but not the trams) using contactless credit cards (Visa, Master, UnionPay) and mobile phone payment systems (Apple, Google, Samsung). (But note that you will mightily annoy people behind you if you faff about for ages with your phone trying to pay when boarding - Octopus just works.)