I have the Netgear R7000, which I bought both because of the reviews, and because there is third-party firmware for it. Both Netgear and Asus are pretty lame when it comes to firmware, only the third-party stuff (RMerlin for Asus, dd-wrt for Netgear) make these routers really usable in my opinion.
So I'm using dd-wrt, which has been stable and reliable for me. Right now, I'm using the latest, 23755, which is working very well for what I'm using on it. Right now, I'm using the core routing and wireless functionality, plus the integrated privoxy for ad blocking. There are a lot more capabilities, when I get around to using them.
The wireless is excellent, coverage and throughput are really about the best I've had here. Somewhat better than the Asus RT-N66U for wireless-n coverage, and I've used the RT-N66U for a couple of years now, so the R7000 with dd-wrt is really doing well. Nice to have the integrated ad blocking as well, since that works for all my clients, wired and wireless. Nice. Not to mention the great dd-wrt web interface, fast and much more complete than Netgear's or Asus's. At the level of RMerlin's efforts with Asus routers (but faster *smile*).
I don't have an Asus RT-AC68U, so you'll have to judge that one for yourself. I've see a lot of conflicting postings here, some are fine, some are experiencing instability. Personally, I'm happy with the R7000 at this point, and the dd-wrt firmware makes a nice piece of hardware very usable.