Arch, because of the AUR and because I can’t get fully used to NixOS. Also, I know my way around Arch better tban any other distro. I tried my luck on Debian and it didn’t go that well, but I’m willing to try again soon. (If only I could get Hyprland on Debian…)
Advantages: has all the software I need, new versions as well.
Disadvantages: lacks a stable branch (I recently found myself with limited/no internet access for about 2 months; if Arch had a stable release, I wouldn’t have had to rebuild my NixOS system over 100 times while I was trying to get a decent DWM setup.