TL;DR: Customers expect to see the Apple Pay instead of the Contactless logo and thus hesitate to use Apple Pay on Contactless terminals. Something to have in mind if your strategy relies on customers being aware of Apple/Android Pay. Just yesterday a restaurant employee told me they support Apple Pay but "it doesn't work above the contactless limit because there's something wrong with the card machine", turned out they don't support Apple Pay.
There's also a State of The Union report for Apple Pay by Loup Ventures (not bad, but not great either).
If you're doing the work, you'll do it better, otherwise, you'll understand it better, either way learn it.