Wireless Performance - more
For the 5 GHz downlink test, the RT-AC56U was clearly the hands-down winner. At 0 dB of attenuation the ASUS router started out at 307 Mbps as compared to D-Link's 220 Mbps and Edimax's 215 Mbps. It never faced a serious challenge at any level of attenuation, leaving the other two jockeying for second and third place. The RT-AC56U finished the test at the maximum attenuation of 45 dB with 15 Mbps of throughput as compared to the Edimax at 3 Mbps. The D-Link lost its connection on the final test.
5 GHz Downlink Throughput vs. Attenuation
Finally, for the 5 GHz uplink tests, you'll note that the RT-AC56U started out the test with significantly higher throughput than either of the other two routers. At 24 dB of attenuation, however, the RT-AC56U dropped a bit just as the Edimax's throughput improved. At 30 dB, the Edimax and the ASUS were neck and neck tracking each other out to the end of the test. At the final test, 45 dB of attenuation, the Edimax was still getting 23 Mbps of throughput as compared to the ASUS' 8 Mbps.
5 GHz Uplink Throughput vs. Attenuation
Prior to the RT-AC56U, I can't remember any product that has ranked #1 in all categories since we started the Router Ranker. But that's what we have with the ASUS RT-AC56U. After reading through the features and comparing AC1200 class routers, I found myself saying, "Wow! I want one of these". This review made start to think that my NETGEAR WNDR3800 was getting a little "long in the tooth".
ASUS RT-AC56U Ranking Performance Summary
All of the benchmarks point to the RT-AC56U being an outstanding performer at the top of its class. But it also carries a pretty hefty price tag of $160. That's a pretty steep premium to pay when most AC1200 class routers are selling for about $100 or even less. For $10 more, you could buy the #1 ranked ASUS RT-AC66U - an AC1750 class router that also ranked as the #1 router in the group of AC1750 routers benchmarked to date. And, for $10 less than the cost of the AC1200 ASUS, you could buy the #2 ranked TP-Link Archer C7 AC1750 class router.
The chart below compares those three routers for the 5GHz Downlink Throughput tests. You can run other comparisons. But from this sample chart, you can see that for either $10 more or $10 less, the AC1750 class routers outperform the RT-AC56U for all data points. Keep in mind that our reference adapter is AC1750 class, so supports the higher 1300 Mbps link rates that the AC1750 routers support. But the shape of the curves say that either AC1750 router should perform the same or better than the RT-AC56U with an AC1200 class adapter.
Comparative 5 GHz Downlink Throughput
Further complicating a cost-based product decision is the #2 ranked AC1200 router, the Edimax BR-6478AC priced at $70. The main downside to that router, if it's a downside for you at all, is there is no USB port on it.
So if you're planning to spend somewhere around $160 for a dualband router, skip a Starbucks or two and go for the ASUS RT-AC66U. Why pay for an AC1750 class router and get only an AC1200? If your wireless needs are more in line with an AC1200 class router, pick one of the other top-rated ones from that class - you'll save yourself about $50-$90.
As much as I like the RT-AC56U, the real problem with the router is its price. Technically, it's all you could ask for in an AC1200 class router. If ASUS had properly priced it with only a slight premium, say $120 street, giving it an unconditional thumbs up would have been a no-brainer.