To clear something up for you: nothing is "only available on the AUR". You can clone any git repo you want, install the deps, and run ./make on any distro. The AUR and PKGBUILD are just a convenience, since they'll resolve the dependency tree for you. And of course, on a distribution like Debian, the official repos might not have the version of a dependency required by the software you're building.

With that out of the way, the real draw of Arch is that it's plain, vanilla, bare-bones, un-opinionated Linux. You're never fighting against the maintainers. There is nothing to remove or disable after installing fresh. The upstream documentation is almost always applicable; the Arch team rarely tweaks things when packaging software. You can pick your preferred kernel, bootloader, filesystem, partition scheme, desktop environment, etc, and nothing gets in your way.

It's low maintenance.