Some Netgear hardware tends to be better than the market, but their software and update cycle is almost always inferior, even compared to some non-Asus routers. They also have a nasty habit of marking their products end of support early or just stopping updates. My own tests with some older Netgear products also showed they are not secure by default (they have open ports that cannot be closed) and ultimately vulnerabilities were exposed as a result. Also, Netgear products (not just routers) started to
collect customer data by default.
Both routers already exceed most client device capabilities. This is why even 3x3 routers remain very popular, with mainly the CPU, software and hardware reliability being the primary differentiators. Most consumers are looking for a device that "just works" for their minimum required features, not for optimal performance.
On top of superior Asus software feature set, the RT-AC86U has one of the fastest and modern CPUs for a consumer router and has the best VPN performance for any consumer router. It is one of the most reliable and least complained about routers. It can also run Merlin, which makes it a big plus around here since this is where RMerlin hangs out.
Finally, it depends on your use case. If you are looking for the best possible WiFi performance from a single unit without having to resort to enterprise APs, then R7800 should certainly be on your review list. But given that these days you can get not just one but multiple SOHO APs for the price of a 4x4 standalone router, even a cheaper one like the R7800, more people are gradually switching to these AP products or re-using routers as APs as they realize in many situations they can get better average wireless performance from wider coverage than from a single router.
So, using multiple APs or routers as APs, devalues the strength of a single unit, especially if its software is much worse by comparison and does not support managing multiple units.
Still, if Amazon reviews are anything to go by, the Netgear R7800 may be 10x+ more popular than the RT-AC86U anyway, though it is a year and a half older than the RT-AC86U. So, pick your poison depending on how you use your router and what you need, not just on a single number.