Either router would serve you well for a GIG connection for WAN. Whether you see GIG over WIFI depends on many variables but I bet you will see at least 600-700 mbs In 5ghz under most circumstances. Home structure and client Hardware wI’ll determine what you get. in optimal enviornments, I saw a review which showed that the 88u pro could get over 1Gig on WiFi…
https://dongknows.com/asus-rt-ax88u-pro-review/
i own the 88u Pro and love it. If I had to make the decision again, I would buy the 88u Pro because it’s only like an extra $50 and its more future proof:
1) Has extra 2.5gps port which is handy for a NAS.
2) Is wall mountable while the 86u is not.
3) Supports 4 by 4 over 2.4.
4) Extra external antenna.
I’ve seen the 88u pro reduced in price by $20 at Microcenter in the past.