Four Stream Performance
Given the RT-AC87U's disappointing performance, I didn't expect much from the R7500 for this test of maximum possible performance from a 1733 Mbps link 4x4 link rate.
I set two R7500's up in open air, six feet apart, one as a normal router and the other in wireless bridge mode. I didn't shut off my in-house 5 GHz network for the test. But it was idle and only beaconing (no traffic). Channel was set to 153, bandwidth mode was in its default 80 MHz mode and everything else was set to defaults.
To keep things simple this time I connected only one computer via Gigabit Ethernet at each end of the bridge. Baseline tests using Ethernet between the two computers and TP-LINK NICs show the Ethernet link capable of a bit over 900 Mbps in both directions with each direction run separately. So the hardwired part of the link shouldn't be a limiting factor.
I ran two sets of tests, one with the antennas on both R7500's straight up and the other with them all set to 45 degrees. The composite downlink plot below shows little performance difference between the two antenna positions.
NETGEAR R7500 four stream downlink throughput
Uplink also showed little difference.
NETGEAR R7500 four stream uplink throughput
I also ran simultaneous uplink/downlink tests for each antenna position. The overlaid plots are a bit busy, but I think you can catch the gist. Total throughput in each case was about the same. Note this test was run for three minutes.
NETGEAR R7500 four stream simultaneous up/down throughput
Because I changed test conditions, I went back and retested the ASUS RT-AC87U pair. I didn't upgrade firmware, leaving the 126.96.36.199.376_2061 firmware used in the previous test loaded. The comparison downlink plot shows both products with cyclical throughput variation. But the ASUS appears to have less and delivers 766 Mbps average throughput vs. the R7500's 547 Mbps.
NETGEAR R7500 & ASUS RT-AC87U four stream downlink throughput
The tables turn in the uplink comparison, with the NETGEAR averaging 624 Mbps vs. the ASUS' 444 Mbps.
NETGEAR R7500 & ASUS RT-AC87U four stream uplink throughput
Composite up/downlink comparison plots were too busy, so I separated them out. Here's the ASUS, producing 871 Mbps of total throughput.
ASUS RT-AC87U four stream up/downlink throughput
And here's the straight-up antenna only plot for the R7500, coming in at 794 Mbps.
NETGEAR R7500 four stream up/downlink throughput - straight antennas
I monitored link rates during these tests and saw mostly 1300 and 1170 Mbps during downlink. I managed to spy a few 1560 Mbps link rates on uplink, confirming that a 4x4 link really was in play. For the ASUS, I was surprised to commonly see 1560 Mbps on both up and downlink and even—gasp—the fabled 1733 Mbps a few times! But if you're expecting to see a solid 1733 Mbps link rate from a pair of these puppies in normal use, I'd say you are dreaming. Even with signal levels in the -30 dBM range, both products, the NETGEAR particularly, had a hard time maintaining four-stream link rates.
I guess I'm going to have to do some comparative testing with AC adapters like the tests recently run with N (Does An AC Router Improve N Device Performance?) to convince people they are throwing money away on 4x4 routers at this point. This time I have evidence, via the above-linked article, that in only one case did the ASUS RT-AC87U produce the most improvement. Your most cost effective bet for moving up to AC right now is an AC1750 or AC1900 class router, which cost at least $100 less.
If you're buying a 4x4 because you believe MU-MIMO will solve your busy WLAN problems, don't hold your breath. NETGEAR was very vague on its MU-MIMO plans with no timeframe mentioned. Last word from ASUS was that it would be shipping its EA-AC87 bridge / AP and enabling MU-MIMO about now. But after very open communication with ASUS during the AC87's launch, lines have again gone dark.
If you simply must step up to an AC2350 class router, the wireless performance-based choice is easy, with ASUS' RT-AC87U/R the better of the two. But if making the most of the bandwidth you get from an overtaxed 10 Mbps or so DSL connection is a priority, the R7500's Qualcomm Streamboost based "Dynamic QoS" is likely the better bet than ASUS' Trend Micro-based "Adaptive QoS". Streamboost has a few years field experience on it at this point, while Trend Micro's DPI engine is still new.
But if it were my money, I'd still buy neither one.