One big difference is that Fastplotlib is based on GPU tech, so its capable of rendering much larger datasets interactively.

How much larger? Holoviz includes the datashader library for GPU-based rendering, and here is an example with 10 million points: https://examples.holoviz.org/gallery/nyc_taxi/nyc_taxi.html

I don't know Datashader that well, but from what I understand, it generates an image from a set of primitives (e.g. points), and then allows you to interactively inspect that image. It does not re-render the points on every frame like Fastplotlib/Pygfx does.

Depending on your GPU, you can render say 1-50 million points smoothly. Also see e.g. https://github.com/pygfx/pygfx/discussions/819

Fastplotlib is very different from bokeh and holoviz, and has different use cases.

Bokeh and holoviz send data to a JS front end that draws (to the best of my knowledge), whereas fastplotlib does everything on the python side and uses jupyter_rfb to send a compressed frame buffer when used in jupyter. Fastplotlib also works as a native desktop application in Qt and glfw, which is very different from bokeh/holoviz. Fastplotlib also has higher raw render speed, you can scroll though a 4k video at 60Hz with thousands of extra objects on your desktop which I haven't ever been able to accomplish with bokeh (I haven't tried it in years, not sure if things have changed)

At the end of the day use the best tool for your use case :)