Aren't you nice. I had read the thread a day or two earlier, but forgot it was mentioned. It must be nice ot have a photographic memory.
BTW, there are a lot of bad reviews for the ASUS RT-AC56U. Yet the Archer C7 was voted best in a test of >20 routers.
Different strokes for different folks.
I can give you a first hand experience of an Asus RT-AC68U vs. Archer C7. I used the C7 (a v1) for about 2 years until I got a T-Mobile Cell Spot from T-Mobile. The Cell Spot is just an Asus RT-AC68U with T-Mobile's special firmware. I reflashed the firmware and turned it back into a stock AC68U and then loaded AsusWRT-Merlin firmware on it.
The only reason I even switched was because I can force the Asus to act as my SAMBA Master Browser with the Asus WRT Merlin firmware and it fixes browser election problems.
Anyway, I could never tell any difference in any speed tests, wired or wireless, with any devices except my Blackberry Z10. 2.4GHz and 5GHz all performed the same in every situation regardless of the router in use. I used WiFi Analyzer to measure the dBi at different locations through the house on my Z10 and on my Kindle Fire HD. The only difference was at the top of a stairwell in the back of my house where the Asus gave me -80dBi on the 5GHz band and the C7 gave me -82dBi. Either one is barely usable at that signal strength.
For some reason, my Z10 will not get more than about .7mbps when it is connected to the C7 on the 2.4GHz band. It has always been that way and it is very consistent. There were some reports that v1 of the C7 also had trouble with iPhones/iPads, too, but my daughter's iPad seems to work just fine. Anyway, they have since had 2 more revisions in the last 2 years and they newer versions don't seem to have any reports of these issues.
Despite the difference in class AC1750 vs. AC1900 there will be no discernible difference in speed between the two.
The Asus has a few more bells and whistles like a dual-core CPU, a better and easier GUI with more customizations and can be made to do a few more things. However, for the average user, the C7 is the most cost-effective choice.
Incidentally, I had to return the Cell Spot when I switched to AT&T last month so it's back to the C7. Chugging along just fine.