You mean in terms of how fast it feels? I have never heard anyone saying this before. Can you share some details and perhaps some tips to improve performance on Nixos?

What hardware do you run Nixos on and do you modify and rebuild a lot of packages on nixpkgs?

Arch and void are very similar except void has a smaller community and much smaller set of packages to install. Arch also has better documentation.

Void is considered more lightweight because it uses runit instead of systemd and a choice to use musl instead of glibc.

I feel for most, arch is a better choice of the three.