Like choosing Debian over Red Hat, or Solaris over Linux, some people just prefer the way it does things.
You can geek out on millisecond benchmark performance comparisons with FreeBSD vs certain Linux kernels, but really it comes down to preference.
I love its design and have been using it on all my servers (and often my home/dev/laptop) since 1998. But that's just me. No need to try to convince you to do the same.