As someone who is not a technical professional, just a hobbyist, I settled on OpenBSD for my server after much experimentation with Linux, FreeBSD, NetBSD.
I like that it maintains a small footprint after installation. No unnecessary daemons.
I like that the code is very well audited. I can trust ftpd, for example.
I like that both userland and kernel are of the same 'source', pun not intended. I don't need to worry about kernel modules.
I like that keeping the system updated means no booting into single-user mode, since I don't have the machine attached to a console.
All in all, I want to spend less time maintaining the box, for what I need. I once read of someone who kept a Slackware box running in his basement without needing to touch it, for years. Now that's freedom, too. In fact, that's my aim with OpenBSD. I love to tinker, but I want freedom from worrying about the thing. Let it serve, so I can have a life