Since there were four AC1900 routers retested, there were multiple ranking changes. NETGEAR's R7000, which was not retested, remained in the #1 spot, but is now tied with ASUS' RT-AC68U, followed by its updated sibling, the RT-AC68P. The TP-LINK Archer C9 moved up a bit and is now ranked above D-Link's DIR-880L, which moved from #2 tie to #5.
AC1900 Ranking Comparison
Comparing Ranker Performance summaries of the two #1 ranked AC1900 routers shows there is more than one way to achieve a #1 rank, i.e. no product is #1 ranked in all benchmarks.
Ranker Performance Summary comparison
Comparing 5 GHz downlink throughput vs. attenuation plots of the four retested routers show a general upward shift in the curves. Note although the Archer C9 doesn't have the highest 0 dB attenuation throughput, it equals or betters the other three routers from 6 dB onward.
5 GHz downlink throughput vs. attenuation comparison - AC1900
The gallery below has a full set of before and after plots.