My impression:

* PF was imported into FreeBSD from OpenBSD, maybe it had problems at first.

* Both implementations have been actively maintained, further developed, and diverged.

* There is now collaboration in the development of the FreeBSD and OpenBSD implementations.

* PF is the shit. Even though IPFW is the "invented here" firewall.

Yep, started on PF and the Palo and NSX FWs I use at the day job are a piece of cake.