I like FreeBSD but i think DragonflyBSD goes the better way in terms of SMP.
WhatsUp and Netflix (https://openconnect.netflix.com/en/software/) also uses FreeBSD, and both of them give something back to FreeBSD:
https://news.ycombinator.com/item?id=8620716
https://people.freebsd.org/~rrs/asiabsd_2015_tls.pdf