Earlier quoted context omitted.
nano is easier than vim to use, so why everyone bother to learn vim then ? Ease to use is not the only thing mater for everyone, and having something powerful, more customizable, more understandable, those kind of things mater to some persons.
You know, my question was serious. There are several reasons for using vim, like maybe you can edit faster if you know the commands, there are more plugins and so on. So if my question had been "why use vim instead of nano", there would have been possible reasonable answers. But what is the advantage of Arch over Ubuntu? They are both Linux... My question was serious, I really don't know why I should prefer Arch.
Your question, now, is a much more open one, then more difficult to answer. This page try to explain the Arch Way https://wiki.archlinux.org/index.php/The_Arch_Way
I wrote something that tried to explain why AUR is an important part of Arch Linux http://www.nicosphere.net/why-aur-is-part-of-the-arch-linux-...