>>506
A full install gives you everything you need to have a productive setup, but the distro also allows for total control over installed software at the same time.
No Soystemd, all package management tools and system services are simple Bash scripts, making it extremely easy to customize how your package manager works and how system services operate.
Rock hard stability, even on the unstable development branch. I'd go so far as to say that Slackware current is more stable than many other distros' dedicated stable versions, like Debian and Ubuntu.
By and far the most traditionally Unix-like of the Linux distros, not using any sort of abstractions over how the system operates, like other distros (namely Ubuntu) do with Systemd and containerized packages OOTB. There's also a dedicated community of third-party package repositories, the most popular of which is SlackBuilds.org (SBo) which offers high-quality community-made build scripts for many packages, in a similar vein to FreeBSD and CRUX ports, and the AUR.
Ultimately, for these reasons (and more), Slackware definitely earns its longevity and pedigree as the oldest actively maintained Linux distro. You can see why I think it's the best :)