It's different than Linux, and mainstream enough to be actively developed and used in production. For a hobbyist, that is useful in itself.

It's a pretty rock-solid system, from my memory of the 2000s.

BSDs in general are tightly integrated between kernel and userland tools. FreeBSD has a lot of modern concepts built in that Linux also has, such as Jails and bhyve VM hosting.

FreeBSD has ZFS has a first-class citizen and in my sysadmin opinion, ZFS is one of the best filesystems ever created. While others dunk on BSD for "catching up to Linux" on certain features, BSD equivalents seem to be really well architected. ZFS is one place where Linux (btrfs) is only beginning to catch up. I just learned about bectl (Boot Environment Ctl) that makes snapshotting and rolling back the system partition of installs really easy, and ZFS-on-root is critical to that tool.

For many, having the simple RC init system is a boon over systemd. Services that need started up at boot are defined in /etc/rc.conf, as well as networking and other core services. Editing rc.conf can be done manually or with the sysrc tool.