To everyone thinking "it's a simple matter of programming" to make the ER show up in the UniFi portal -- if it was, don't you think UBNT would've done it already?
-- both are decent routers. Personally, I prefer the EdgeMax line over the UniFi line, for the simple reasons of "it's easy to get complex things done with". Sure, the USG is a great router, and you can do cli-style configuration with it, but it's not a simple matter of "configure / add config / commit / save" as with the EdgeRouter line; you have to export the config, and then put it into the controller so that the controller doesn't overwrite it.
If you're looking for a router for a "simple SOHO" setup (e.g. standard locked down / simple port forwarding), it's probably a wash.