[ch_123]

The "lightweight" nature of OpenBSD is a matter of perspective - if you are happy with OpenBSD's feature set, then it's a plus. On the other hand, FreeBSD has a lot of additional features, including ZFS, which may be of interest. The last I checked, FreeBSD was more performant in various benchmarks, particularly regarding multi-core performance.

[dijit]

FreeBSD has a bit more of a lax attitude historically to security[0] and seems to prefer being reasonably performant and "easy to use" (this is subjective, but they care about supporting packages outside of base very much, and bundle non-FreeBSD produced packages as part of their base).

OpenBSD on the other hand is perfectly happy to leave oodles of performance on the table for security. They were the first OS to completely drop Hyperthreading support for example, years before spectre/meltdown.

So with these things in mind, FreeBSD is a lot more performant.

[0]: https://vez.mrsk.me/freebsd-defaults