Initial goal was to setup an SSH jump host with Debian. Then the realization that I don't actually need all the extra bells-and-whistles, just something that is designed to be secure out-of-the-box: OpenBSD.

Some features of OpenBSD that makes it attractive:

• Documentation has been praised to be complete and well-written.
• Userland software are more tightly integrated and coherent.
• Exploit mitigations are enabled by default.

And then the disadvantages:

• Likely outdated design (e.g. this article focuses on missing MAC implementation on OpenBSD, some assertions on, say, LPE are not limited to OpenBSD, but overall still valid).
• Less hardware compatibility as well as online help, i.e. less modern.
• Anything beyond the core suite of services provided by the base system will inevitably introduce vulns.

Misc

Other comments on FreeBSD, including the good and the bad (mostly security-related). FreeBSD is probably more commonly used as a daily driver, and thus has more traction, e.g. FreeBSD new user guide.

Guides for new users to OpenBSD:

• OpenBSD FAQ. As authoritative as you can get (see also Migrating to OpenBSD)
• Some blogpost: A nice perspective into OpenBSD from Linux.
• OpenBSDHandbook: Unofficial guide for OBSD, with much content lifted from the original OpenBSD FAQ.