There really isn't /that/ much difference between BSD and GNUs user space. And definitely nothing that can't be found out after spending a few seconds in Google or the UNIX man pages.
Plus FreeBSD docs are excellent (in fact I've found them to be a more reliable source than even Ubuntu's - but that's a whole other topic)
It's fast like Slackware (which I liked when I tried it), very customisable by using PKGBUILD/AUR (similar to Gentoo portage, which is amazing for absolute control) and has an excellent wiki (https://wiki.archlinux.org/).
You'll also get the most up-to-date packages, and roll along happily.
If you feel you need a little more stability, then go with a Gentoo or Funtoo Stage3 install. :-)
Re FreeBSD, the best thing about it is the Port system, but you'll likely be hating the non-GNU userspace!