Pro As slim or copious as you want it
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.
Pro Fast and simple package management
pacman works much faster than apt-get or yum due to better mirrors than other distributions tend to select by default. There are fewer default repositories to download from though all package management is combined into one tool instead of being split into dpkg, apt-get, and apt-cache like on Debian distros.
Con Not for the faint of heart
Arch only holds your hand a little bit of the way. While documentation is great, you are expected to know what you're doing. The result is that when you find the solution for a problem on a forum or elsewhere, the response may be completely over your head. If you're not well-versed in Linux, what would be a minor issue on another distribution can become a drawn-out research project on Arch, as you learn all the inner workings of the operating system, until you understand it well enough to solve your problems yourself.