The main factor determining the choice between NFC or Bluetooth is the transmission distance.
To exchange photos and videos between two smartphones, or connect with another device (headset, speaker, household appliance), Bluetooth is much more interesting.
With so many potential connections, the risk of interference between unintended devices is significant. How is this problem solved? The Bluetooth standard requires an initial, manual association step (pairing) for two devices to start communicating with each other.
This association step is obviously problematic in the context of contactless payments, which require speed of execution and, above all, the possibility of interacting with any device.
The difficulty is solved by the low-distance communication capacity of NFC, which is 10 cm and works best within 4 cm. At such a small distance, interference from another device has almost no chance of occurring.
NFC therefore allows any device to interact quickly without prior association, while guaranteeing safety through the short reading range.
An additional level of security is applied by the payment software requiring the user’s authorisation via code entry, fingerprint or facial recognition.
Another relevant factor is the data transmission speed which is relatively low (424 kbps) for NFC, but fast enough for the transmission of a few kilobytes of information (card number, cardholder). Such a low speed is not suitable for large amounts of data like continuous streaming of sound, as in the case of wireless headphones.
Lastly, note how NFC and Bluetooth differ on two-way communication. A mobile device using these standards assumes the dual role of receiver and transmitter, while NFC (based on RFID technology) on contactless cards only communicates one way.