FreeBSD + pf is hands down my favorite combination for simple packet filter firewalls. Been that way for a long time.
I mean, I definitely love that OpenBSD is the "reference" implementation of PF, but the network performance definitely lacks a bit and UFS is quite outdated and prone to errors on outages. ZFS has the upper hand there and FreeBSD's network performance.
And adjusting from the reference PF to the minor differences on FreeBSD's version is not too bad.