> MacOS is still a second-class citizen in the Nix world and a fair amount of stuff doesn't work properly

In my experience:

With fewer nix users on macOS, it's more likely you'll run into software which isn't in the binary cache, & so will compile from source. (brew also does this).

With fewer nix users on macOS, it's may take longer for packages broken on macOS to be fixed.

It's a bit more of a hurdle to use .app programs out-of-the-box compared to brew, due to the symlinking.