Personally I'll stick to my RB4011 for routing purposes. Comparing an USG3 to a RB760 the RB760 beats the USG3 hand down. I can't compare my RB4011 with a USG-Pro as the 4011 is capable of 10Gbps.Personally, once my stuff is setup, I only look at it when I want to update it.
Havent used Unifi (just have an AP that I never touch except updates) and their shiny UI, but for the money paid, the Mikrotik stuff is insanely flexible.
Want to see whats going on on an IP or an interface? Just use torch. You can see every single connection thats happening live. The queues are also super easy to set up.
I set up a master simple queue, then a sub queue for my mibox, sub queue for one or two specific devices, then a sub queue for everything else on the network. Each has their own priority and throughput ruleset. No mangle or funky rule's.
Thats about all I need out of it for now and it does everything I need.
One thing that might help you decide is look at what feature set you need, and what performance you need. I know for a fact that if you switch on all the bells and whistles on the Ubiquiti USG that the max throughput is around 85Mb/s. If you want those features for more performance you have to get the USG Pro. Not sure how Mikrotik stacks up when going toe to toe, but sure the guys here might be able to help.