Recs.
Updated
SpecsUpdate
Pros
Pro Highly customizable while keeping stability
Devuan is stable in a similar way to Debian, giving many customization options to the user while keeping itself stable.
Often you will be quickly able to install many features such as your favorite WM and shell without any hassles, working as intended.
Also, much like Debian it allows the user to opt out of any non-free packages if they choose.
The keyword of Devuan is option.
Pro Good for old machines
Devuan's direct mirroring of Debian's rep means it is a great systemd-free distro to bring back legacy hardware from the dead, they keep many legacy drivers and packages in their repository.
Also, many of Debian's available guides in the internet apply to Devuan as well (as long as they don't mention systemd-dependent options), so you will have an easy time finding a way to configure your 10+ years old machine with Devuan.
Not to mention, it is possible to do minimal install of Devuan (installing, step by step, what you want and/or need for your old computer).
If bringing back an old PC is what you're after and you want/need it to be minimal/fast/stable, then consider Devuan.
It may help your old Desktop to keep up with modern standards to the best of its old hardware capabilities.
Pro It's Debian
Devuan is Debian just without systemd, it just mirrors the the Debian archive and repacks packages that have hard dependencies on systemd.
Pro Most decent look amongst other XFCE distros
Default XFCE theme is unique of all the XFCE distos including MXLinux, Xubuntu etc.
Cons
Con Installer on Devuan is very poor
Devuan doesn't install on HP Z840. It's possibly due to it having too many processors and confusing them. Ubuntu and SuSE, both with systemd install and run, but slow as a snail, as you'd expect. It's best used on old machines that Devuan's simple installer can handle. It is quite a shame, quite a shame!