I don't have UAP-AC-PRO, but have UAP-AC-LR and I absolutely will stand behind stating that they are superior in stability than the Asus routers they replaced.
Are they as fast on single client? Nope, Asus wins. My Asus was a 3x3 AC device while my UniFi are just 2x2...so easily have speed differences.
Are they plenty fast with multiple clients? Yep, UI wins.
Can I centrally manage them? Yep, UI wins.
Do I have to reboot them on a regular basis? Nope, UI wins. The only reboots these get are due to updates or power outages.
Do they look like odd alien spiders? Nope, UI wins. They look like big smoke detectors and could easily be in visible locations without much notice.
Do I have to have a wall wart nearby to power them? Nope, UI wins. PoE is great...when it works correctly.
Did I have to spend a fortune on them? Nope, UI wins. A single BFR will "usually" cost north of $200 (not always...prices are all over). While I can usually get 2-3 UniFi (or TP-Link) devices that can be better distributed.
In my use case, the PRO didn't bring enough value to party to justify the price differences. So I landed on the LR and InWall for my house. They can be out in the open without my wife being highly annoyed (they still annoy her, but she mostly tolerates them to an extent) while my Asus was required to be hidden and completely out of site. They are distributed across the house so I have decent performance in 95% of my house instead of 50% decent, 25% marginal, and 25% dead zone.
Again, it really depends on your use case which solution is right for you. A single BFR may work for some, but it for sure doesn't work for me. Having cheaper distributed radios makes way more sense from an RF perspective to cover my needs.