The base build system (build.sh)[0] which is essentially Makefiles is absolutely beautiful to work with, ditto for pkgsrc[1]. They’re “progressive” enough to include dtrace[2], work on neat security[3], and kernel models[4][5], but have eschewed modern Linux-isms like ip(1), systemd. Of BSD v Linux, my heart is definitely with the more traditional BSD. Of BSDs, I feel Net is capable enough, simpler than Free, but more feature full than Open. The other interesting BSD would be DragonFly - really interesting, but I’m happy enough w Net that I’m not going to swap it out, and don’t need more (different) systems in my life right now.
[0] https://www.netbsd.org/docs/guide/en/chap-build.html
[1] https://en.wikipedia.org/wiki/Pkgsrc
[2] https://en.wikipedia.org/wiki/DTrace
[3] http://www.netbsd.org/support/security/