Both connection types are genuinely reliable when set up correctly — the real question is which one's failure modes fit your setup better, since each has weak points at different moments.
USB: consistent, but tethered
Once connected, USB rarely disconnects unexpectedly and doesn't suffer from interference or pairing issues — its main limitation is simply the cable, which restricts how far the printer can sit from the device and rules out a fully mobile setup.
Bluetooth: flexible, but occasionally flaky
No cable means the printer can sit anywhere within range, which matters for a mobile stall or a tablet-based counter — the trade-off is occasional dropped connections, especially with interference from other devices or distance from the paired device.
For a fixed counter, USB is usually the safer default
If the printer and device both live in the same spot permanently, USB's stability outweighs Bluetooth's flexibility — there's little benefit to wireless when nothing is actually moving.
For a mobile or multi-location setup, Bluetooth is often necessary
A market stall, food truck, or roaming staff member with a tablet genuinely needs the flexibility Bluetooth provides — the occasional reconnect is a reasonable trade for not being tethered by a cable.
Whichever you choose, keep a backup plan
For high-stakes moments (a busy shift, an event), knowing how to quickly reconnect or restart the connection avoids a stalled queue if the printer briefly drops — a two-minute fix beats an unprepared scramble.