I was looking at pf sense last night, and wondering if is it really better than a stand alone router at tasks like this. Routers have dedicated hardware optimised for these tasks where as a pc does not, so does it really bring an advantage to use pfsense?
It's more the other way around. Having dedicated processing for routing etc on-board allows them to use silly small specs, for example a 500MHz CPU with 128MB RAM. That's great for a little low end gateway and DHCP server, but for anything 'proper'?...
Any self-built machine for pfSense or similar will have ample hardware grunt for even high end routing etc. You can build a quad, hex or more core system with 16GB, 32GB or upwards of RAM in a tiny mITX box with a laptop wireless card, quad port NIC and m.2 SSD pulling 10 watts under full load while routing gigabit+ on the WAN.
Good luck trying to run a UTM on a commercial plastic router box.

With a small self built system you could run pfSense or Sophos UTM Home (both free) with built in routing, firewall, IPS, antivirus, antispam, squid proxy, filtering, endpoint protection, VPN server and client, mail server, domain directory, web services and God only knows what else. Much better! I'm just about to build a new one.