I use OpenBSD for most of my servers, with FreeBSD mixed in too. It is very simple to administer, easy to upgrade (sysupgrade every six months, syspatch otherwise), reliable, and fits how I like to administer it. Pf on OpenBSD has pf auth which allows unblocking ports for users who have sshed in, which is nice when you are on a dynamic IP. It is generally just a nice system, minimalist, and straight forward. I don't want a million moving parts, just a UNIX platform to build on.