Now that the AX vs. AC performance for each product has been shown, it's time to put the products head-to-head.
The first 2.4 GHz downlink plot compares all five products with the Intel AX200 STA. All show higher throughput from the higher AX link rate except the Qualcomm-based NETGEAR RAX120. As noted earlier, the STA reported the expected 287 Mbps link rate at the start of the RAX120 run. I don't know why throughput didn't follow the higher link rate.
AX STA Throughput Comparison - 2.4 GHz Downlink
The same conditions, but with the Qualcomm-based Pal24 configured as an AC (actually N) STA shows the Intel-based NETGEAR RAX40 as the outlier. The RAX40's different performance with low atteuations (higher signal levels) is likely due to poor rate selection.
AC STA Throughput Comparison - 2.4 GHz Downlink
The 2.4 GHz uplink plot with AX STA shows the Intel-based NETGEAR RAX40 having the lowest plot. Since the plot falls off faster than the others as signal levels drop, I suspect we're seeing the effects of the RAX40's two-stream radio vs. the four-stream designs of all the other routers.
AX STA Throughput Comparison - 2.4 GHz Uplink
Switching to the AC (N) STA plot doesn't show the same weakness for the NETGEAR RAX40. All products produce essentially the same results.
AC STA Throughput Comparison - 2.4 GHz Uplink
Moving on to the 5 GHz downlink plot with AX STA, we see the widest range of results. It appears that the Qualcomm-based NETGEAR RAX120 turns in the most normal performance. followed by the Intel-based NETGEAR RAX40. All three Broadcom-based routers do not perform well in this benchmark, but show remarkably similar RvR curves.
AX STA Throughput Comparison - 5 GHz Downlink
The same benchmark using an AC STA again shows the NETGEAR RAX120 as the best of the bunch. The RAX40 doesn't fare as well this time, with throughput oddities at both start and end of the run.
AC STA Throughput Comparison - 5 GHz Downlink
If I had to declare a winner for 5 GHz uplink with AX STA, it would probably be the NETGEAR RAX120. It had the most well-behaved performance and highest starting throughput. Note that all three Broadcom-based routers did not behave the same in this benchmark, with the most expensive ASUS GT-AX11000 showing the widest variations with strong to medium level signals.
AX STA Throughput Comparison - 5 GHz Uplink
Finally 5 GHz uplink with our AC STA shows the least desirable behavior from the Broadcom-based ASUS RT-AX88U and Intel-based NETGEAR RAX40.
AC STA Throughput Comparison - 5 GHz Uplink
This is a lot of data to absorb, so how about some key takeaways to help digestion?
In general, 2.4 GHz AX performance was better behaved than 5 GHz. Most products produced around 2X throughput when used with an AX STA vs. an AC STA. Right now, this is likely to be the thing that most buyers would notice from upgrading both router and device to Wi-Fi 6. Note that you'll get this benefit even from using 20 MHz bandwidth and even with the lowest priced two-stream NETGEAR RAX40.
There was no throughput gain observed from AX vs. AC when using 5 GHz. Even though our test STA got the expected 1201 Mbps link rate with all routers with the strongest signal, this did not translate to higher throughput. In fact, both AC and AX STAs were only able to get 700 Mbps at most and usually below that. 5 GHz uplink with the AC STA actually produced the highest throughput!
5 GHz downlink performance with both AX and AC clients needs work. Only NETGEAR's Qualcomm-based RAX120 and Intel-based RAX40 produced anything remotely resembling a normal RvR curve. The RAX120 was best behaved with both AX and AC STA running downlink and uplink. 5 GHz uplink was generally better for both AX and AC STAs for Broadcom-based routers, but was not without problems.
Even after almost a year after the first products started shipping, Wi-Fi 6 remains very much a work in progress. Key features (OFDMA, AX MU-MIMO, Target Wake Time (TWT)) are still not enabled by most products and, if these tests are any indication, you're unlikely to see performance gains in from 5 GHz.
If you have AX devices and feel you must upgrade right now, spend as little as possible. Until OFDMA is enabled and we see whether that helps bring more bandwidth to busy WLANs and reduce latency, there's no sense in making a large investment that may not pay off.