Although Arch Linux only comes with around 10,000 packages, you can use the Arch User Repositories (AUR) which will add over 50,000 more packages.

The AUR is a repository with a very extensive catalogue of build/install scripts that are contributed by users. While these scripts are inherently less secure than conventional packages maintained by a distro's authors, it's still way easier to verify the security of install scripts than it would be to write them yourself. It's very usefull.

Arch keeps its core repositories slim and free of unnecessary dependencies. At first installation only a bare system is set up. You can easily get the other applications through the package manager. The repositories are nearly as full as those of Ubuntu, while they are often more up to date. That way you don't have to waste time with software you don't need or want.

Pacman has performance advantages over apt-get and yum in both database operations (thanks to being written for speed) and download times (by virtue of using better mirrors than other distributions tend to select by default). There are also fewer default repositories to download from, and all package management is combined into one tool instead of being split into dpkg, apt-get, and apt-cache like on Debian distros.

If you need to install something, chances are someone in the Arch community has already made a package for it. This makes it incredibly easy for you to install and maintain all of the non-media content on your computer.

Arch Linux follows a rolling release model, which allows users to stay on the most up-to-date versions of the software they are using.