If you look carefully at what i said is that most VPN routers had unstable firmware with that platform and even ubiquiti also did have unstable firmware up to a point. However even the ERL is clocked almost twice as much as the higher end cisco RV. So for a router that isnt usb powered/portable having that extra frequency helps a lot. Although ubiquiti has gone far to improve their firmware that it is so far the only stable firmware i've seen for that platform, cheaper than the cisco RV while offering more but also higher clocked.
There are also 8 and 16 core variants of the Cavium but i havent seen them used anywhere yet and UBNT has no interest in software NAT performance, they're very reliant on hardware acceleration when most of their customers get an edgerouter for the very reason that it is a cheap configurable router expecting it to perform well in their environment, usually involving multiple users, organisations, businesses, etc. I like that you can install debian software on edgerouters as long as its compiled for MIPS but the lack of CPU is a concern. The Cavium MIPS CPUs are good but a lot of it badly implemented. If a router manufacturer wishes to reduce the power and heat usage than dynamic clock scaling would really help so theres no reason not to use higher core counts and higher frequencies.
While a dual core Cavium MIPS at 1Ghz can do about 160Mb/s of squid im not sure how well broadcom's ARM A9 actually stacks against it.