Oh, yeah, there are others, aren't there. Heh, kinda jumped the gun there.
NetBSD seems to be the operating system of choice for those who just like to hack on OSes. It's clean, portable, fast, and friendly to those who like to play with the guts of the system. If you enjoy re-designing messy complex systems into cleaner complex systems, NetBSD is the choice for you.
Depending on the task, I recommend one of FreeBSD or OpenBSD. OpenBSD is very secure, fairly stable, very simple, and very specific. FreeBSD is moderately secure, very stable, extremely complex (but not needlessly so), and quite general.
I recommend using OpenBSD for the following tasks:
I recommend using FreeBSD for the following tasks:
My network requires all of the above tasks for both OpenBSD and FreeBSD, so I have two systems. The OpenBSD system sits between the big, bad Internet and the rest of the network; routing, firewalling, proxying, and generally being secure. On the inside of the network is my server, acting as a Web, FTP, and database server (and my desktop). Thanks to this setup, I don't have to care about security on the servers and other computers on the network, and can instead put all the protecting effort into one computer.
When you're not putting out fires on the server or breaking everything on your test system, you want something stable that just works. For this I have two recommendations: macOS and FreeBSD.
Many people forget that macOS is a BSD, but its kernel comes straight from FreeBSD! Don't be fooled by the pretty GUI and the fact that things just work in it; this is a unix.
A downside, and the reason why I wouldn't use it, is its license sucks. It's not Free Software, or even Open Source; this is a proprietary system. Don't change the code because it's illegal.
Another downside is that it currently only runs on the PowerPC architecture. This means that those cheap x86 machines that you find in the trash won't run macOS. However, Apple hardware just plain rocks.
Rumor has it that these make awful servers. If you're the type of person who just wants something to chat with your friends, check your email, browse Web sites, or develop graphics, then macOS is for you. Else, keep reading…
If you're an end user like I'm an end user, then all that means is that one of your servers also has X on it. If you play with Web servers when you're not playing with Web servers, then FreeBSD is the desktop system for you. It has way too much software available for it, all of which is trivial to install. The GNOME2 port is probably the best maintained piece of software, ever. Programming languages such as Ada, Haskell, OCaml, and C have large communities of support. More multimedia devices are supported than in OpenBSD or NetBSD.
Both downsides of macOS are fixed in FreeBSD: the license is the too-liberal BSD license (minus advertising clause, of course); it runs on seven different platforms, including 64-bit Intel, 64-bit AMD, 64-bit Sparc, Alpha, MIPS, NEC PC-98x1, and, of course, x86.
I run OpenBSD now on everything. I've edited some of the above with some reflection of that, but I've overall left the content as-is.
These days I'd probably recommend FreeBSD to people who don't want to think too much about their computer, and OpenBSD to software developers with a curiosity for their OS. Apple's OS is BSD in law but not in spirit and not really something I can recommend.
Though, what is the point of this article? Who is the audience? I can't imagine someone asking, “I know nothing about this topic but I hear great things about any BSD operating system. Which should I use?”