Qubes is good for using one computer to satisfy multiple threat profiles. E.g. if you want to shitpost on Facebook, visit shady websites, and ghostwriting for a controversial magazine _all without linking those three activities_, then Qubes is the OS for you.

If you want to dedicate one laptop to a very specific anonymous activity (e.g. being a ghostwriter for a controversial magazine) _and nothing else_, Whonix is the OS for you.