alt Hacker NewsThe key here is the "PIO" which you won't find on a Teensy. It lets you do extreme "bit banging" tricks including generating video. People have even implemented Ethernet on it. I've used it for some custom serial protocols ("Weigand") used by alarm panels.
Really I guess I don't know what that is then as I buy the Teensy since it has so much IO, multiple UART, multiple I2C busses, sd card reading, etc...
edit: interesting
(Teensy | Pico)
Special Features: CAN Bus (3x), SDIO, S/PDIF | PIO (Programmable I/O) (8 SMs)