Been using sway for many years before moving to niri last year.

Outside of the fundamental window management differences, I find that a lot of stuff with niri is easier to make work, or just happens to work out of the box. Screen sharing with sway was always a problem for me[1], whereas for niri it works great (incl. sharing individual windows only[2].) I also found that niri is much better at letting hardware go to sleep (which saves 10W on my GPU.)

[1]: https://github.com/swaywm/sway/issues/7898 etc.

[2]: https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3864