First of all, after transferring the card from the physical card to Apple Wallet, I did not receive the HKD50 deposit refund at all. Customer service is absolutely useless in providing a solution as well.
Additionally, I have noticed that from time to time, the MTR gate fails to recognize the this app express transit payment and instead conflicts with the Visa payment, when it happens, you'll be THAT person clogging up the gate with a long queue behind you giving you the dirty look, I would advise tourist to simply keep to using the physical card to avoid this headache.
Last but not least, you can no longer top up with cash if you use the Apple wallet version, since you can't insert the card into the top up machine. This tourist app charge a higher conversion rate.