Depending on your use case and patterns, OpenBSD may be completely useful or totally lacking; it doesn't have bluetooth, you're not going to be able to use proprietary software or play many games, and the smaller community and tighter security standards make the available pool of ported software smaller. However, it has great laptop support, an extremely cohesive and well-documented userland, and a very simple and easy install/upgrade process.
FreeBSD can basically replace Linux for any usecase except laptops, because it's power management kinda sucks. It has optional Linux binary compatibility, WINE, the bhyve hypervisor, ZFS support, FreeBSD jails, more ports than many Linux distros, and a decently cohesive userland. I far prefer OpenBSD for actual daily use, but FreeBSD is perfectly usable.