Better embedded GPIO. RPi Zero is a great little board/computer but the capabilities of the GPIO pins are lacking in a lot of ways. Speed being the biggest problem.

This little $8 board will run circles around even an RPi 4 when it comes to doing something like controlling a long strip of ws2812b RGB LEDs, as an example.

>run circles around even an RPi 4 when it comes to doing something like controlling a long strip of ws2812b RGB LEDs

Why would a Raspberry Pi have any issue with this?

Linux and it's lack of hard real time functionality. ws2812b's don't have a clock signal and instead rely on relatively tight timing of the data to seperate the bits. So you end up having to write a kernel driver to either disable interrupts as you bit bang GPIO, or take over a SPI device and set it up with nasty parameters to get a ws2812b waveform out of the MOSI data line. This chip can simply dedicate one of the MCU cores to the task of babysitting that interface.

Currently, RPis are quite difficult to obtain and have been since 2020. I was just looking at a project design that required 2 RPi Zero 2 Ws and I'm currently considering alternatives. Unfortunately, the software stack is Java, so I don't think this will work.