Objective WiFI is grossly affected by the specific environment that it used in. People tend to talk about things in rather subjective way and will not take into consideration that other might have different situation that is Not part of the technology pre-se.
Otherwise most users knowledge comes for Marketing and advertising gimmicks, and self-inflicted psychological status.
When you read technical data the xr500 and the ac88u are very close in performance.
I would read carefully all the features and choose the One that is the closet to what I need.