Also worth adding that the ERL runs EdgeOS, which is actually a fork of Vyatta 6.3 with some added features and certain hardware accelerations. [1]
Vyatta was acquired by Brocade in 2012, after which the community edition was sidelined and the main product became closed source. Thankfully Vyatta core was forked in 2013 and re-branded as VyOS (free and open source) and is under active development. [2]
I've used pfSense in the past and VyOS currently and found both to be excellent.
[1] https://community.ubnt.com/t5/EdgeMAX/EdgeOS-vs-Vyatta/td-p/...
How much power does the ERLite-3 use? I've run PCEngine APU (http://www.pcengines.ch/apu.htm) boards with pfsense and it's worked great with very minimal power usage. Although they are usually a bit more expensive than an ARM board.
I ran pfSense for years, and it does work great, but an x86 box running all the time just to do what a little 2-decks-of-cards box can do with 1/10th the power seems silly these days.
http://wiki.gentoo.org/wiki/MIPS/ERLite-3