FreeBSD vs Plan 9

Ports provide a wide collection of software which are easy to build, install and modify. They contain recipes and patches to build various software, so you can simply run "make && make install" to build and install the software. You may also keep local patches and it would be picked up automatically. It also allows you to use the latest software even if you are not using the latest version of the operating system.

Base system contains basic developer tools, including compiler, debugger and system utilities.

Jails allow for partitioning a system into several independent "mini-systems", a feature not found in many of the popular OS choices.

FreeBSD won't change everything from a version to another, it tries to keep and maintain old tools as long as possible, and won't replace half the system every two versions like GNU/Linux distributions such as Ubuntu, Arch or Fedora does. everything is stable and also pretty minimal. FreeBSD is designed for performance.

Plan 9's design is very orthogonal and well done.

With Plan 9, computers are turned into terminals where you can access files and processing units which can be located elsewhere. Data storage is handled by another external server. This means that instead of each person having their own individual computer with all the required parts, all of the computing and storage is done in a central area and everything is networked in together.