Paypal is taking on Apple and Square with a growing number of acquisitions. Paypal recently bought Venmo and using QR technology they have been working with various retail operations.
Apple Pay uses NFC for bank cards. Debit cards and credit cards galore are supported and most cards also work on the Apple Watch.
QR is used with some restaurant apps such as Starbucks and Subway. Both are gift card based but Subways app supports a credit card for payment. I tried the Starbucks Watch app and it was successful.
I use Square which works with my iPhone via Bluetooth for receiving payment for services. More recently Square introduced a stand-alone terminal with integrated printer that uses Wi-Fi making it easy to integrate into a business.
Square has been moving into web payments with their banking system. This is slightly faster than PayPal in terms of transaction and credit in the bank for disbursements.
PayPal wants to horn in on the action with an alternative payment processing. At present their app is more of a transaction record similar to bank and credit union apps but many US retailers are still using bank cards,
Recently PayPal bought iZettle which is the EU equivalent to Square. iZettle started in Stockholm.