The main reason to use Linux is because almost everyone else is. If you're only installing it on your own servers at home, then that's okay. But in a business environment, the minor differences or improvements with FreeBSD are simply not worth the lack of familiarity for most people over Linux.

I used FreeBSD starting in 1999-ish and I still have the original Design and Implementation of the 4.4 BSD Operating System on my shelf. I used FreeBSD exclusively for years, but it has completely lost to Linux and Linux frankly is good enough.