I personally use Manjaro, because their releases hold back slightly from the Arch release cycle, resulting in (in my experience), a more stable experience. As far was why Arch? With any Arch distro that has Pamac installed (The GUI for pacmac), you have a fully graphical software repo that is easy to navigate and operate. In addition, you get new packages quickly after release rather than waiting on a release cycle, whatever that may be. Arch has perhaps the most documentation of any distro on the web except MAYBE Debian. But perhaps the biggest reason to use Arch based can be summed up on one word: AUR. The AUR has anything and everything you can imagine. It's like PPAs that doesn't suck.