Pfsense is such a great piece of software, DNS forwarder and build in OpenVPN.
Is there any reasonable explanation for their choice? I'm using FreeBSD myself but not as a router. If I should choose an OS for router, I'd probably go with OpenWRT or OpenBSD.
Another lover of PFSense here. I started out with M0n0wall, but there were a few items that drove me to pfSense ultimately (the slightly strange way setting up rules/port forwards, and the need for different IPSEC encryption algos for a corporate firewall connection.) I have pf humming along on an older Alix2d3 kit, and have had ZERO problems. I now see that there's a more powerful APU board that will be my upgrade path when this box dies, or I upgrade my internet beyond ~50mbps -- whichever comes first.
The statement that the "pf" in OpenBSD is "better" isn't necessarily true. The "pf" in FreeBSD and pfSense is a bunch faster, even on single-core.
the IPsec in FreeBSD and pfSense (especially AES-GCM) is also, much faster than that found in OpenBSD.
OpenBSD has a problem: it doesn't scale on multi-core CPUs, and the world has gone multi-core. FreeBSD took years to get this right (forking Dragonfly along the way due to disagreement about the MT model.)