Not interchangeable, and neither one covers every reader. USB has the
headroom — a full frame over Bluetooth costs a second or more, against a
reader pressing arrow keys several times a second — and needs no pairing and
no charge. Bluetooth is the one that works on Android, where Web Serial does
not exist, and the one that leaves the desk free of a cable. So both are
offered and the reader picks.
hid is the third, and belongs to a different kind of device: a braille
display speaking the USB HID braille standard, as a Monarch does in Braille
Terminal. WebHID reaches it whether it is on a cable or paired over
Bluetooth with the computer, and cannot tell the page which, so it is one
transport rather than two.
How MAIDR reaches a tactile display.
Not interchangeable, and neither one covers every reader. USB has the headroom — a full frame over Bluetooth costs a second or more, against a reader pressing arrow keys several times a second — and needs no pairing and no charge. Bluetooth is the one that works on Android, where Web Serial does not exist, and the one that leaves the desk free of a cable. So both are offered and the reader picks.
hidis the third, and belongs to a different kind of device: a braille display speaking the USB HID braille standard, as a Monarch does in Braille Terminal. WebHID reaches it whether it is on a cable or paired over Bluetooth with the computer, and cannot tell the page which, so it is one transport rather than two.