Compared to Arch(-based): Accesing the latest packages. It’s not impossible, especially if you go for Debian testing repos, but it’s definitely extra work.
Compared to special-purpose distros (i.e. gaming, portable, high security/privacy, pen-testing): Whatever their special purpose is will usually be harder to achieve.
Compared to huge corpo distros (SUSE/Fedora and derivatives): Ease of more intricate setups and maybe some security testing.
Compared to Ubuntu: Paying a corporation to not withhold security patches from you.
waydroid (if you don’t install a wayland based de)
Nothing
Running alternatives to Systemd.
Y-you’re not supposed to ask that!
You can’t have your entire system configuration in a repository of plain text files, which has lots of advantages, but it’s not worth caring about unless you feel excited to get into it.
Found the other NixOS user. ;)