FreeBSD has a simple and consistent upgrade path between major releases, excellent stability, excellent hardware support (on the server side, at least; that's where it matters to me personally), a magnificent packaging and ports system, excellent documentation, an excellent firewall stack (pf), a proper ZFS implementation, a powerful and easy-to-manage jails system, and is used in plenty of corporations, large and small, both as a conventional server platform and as a base for commercial products.
It is a well-curated shop, while GNU/Linux is a street bazaar.
It is a pleasure to administer.
You might want to take a closer look.