When it comes to tooling, I found the packaging strategy of Arch to be pretty invaluable, too:
- Pacman is a great package manager (esp. when compared to e.g. ´yum´).
- The Arch User Repository (https://aur.archlinux.org/) has a large list of additional packages maintained by the community.
- The PKGBUILD format used by the AUR is easy to read and essentially just generates Pacman packages you can install alongside packages from the Arch repo.
- PKGBUILD also makes it really easy to create a package for some obscure software yourself (or e.g. a specific font), if necessary.
- There are tools that create PKGBUILD packages from language repos like gem, npm or pypi (via pip). Those are really useful since they prevent language based packages from clashing with pacman.
In addition, I really like that arch is built with choice in mind: There's no default "way to go" - you can e.g. choose from several desktop environments without having to install a specific one first, meaning you can configure your system from the ground up.
I think Slackware and Gentoo work similarly? (I've personally never tried them)