NetBSD: Created and run by people on a huge variety of computers, big in Japan.
OpenBSD: Created by its own users, fork of NetBSD, run by everybody who truly cares about security and correctness.
edit: I have other systems. I agree with OpenBSD.
One great example is wifi, you create one config file in /etc/ for each interface, and then decide how you want it to be handled. To control wifi, you use ifconfig as you would any other interface. Why not just treat it as an additional interface and make it work with all the normal Unix type utilities and workflow?
This is correctness.
OpenBSD - You care about security
NetBSD - You want to hack on BSD
I run NetBSD on a system with 24 megs of memory. I don't think this is possible with modern GNU/Linux - one would need an older kernel and something other than systemd, I think.
"I am on x86-64 and I want performance".