Performance - more
5 GHz downlink shows the extender link with high variation at the start of the run, then settling down. Extended throughput is 34% lower.
NETGEAR EX6150 throughput - 5 GHz down
The 5 GHz uplink plot is the clearest example of expected extender throughput, with the extended link 47% lower than the extender.
NETGEAR EX6150 throughput - 5 GHz up
I also tested the EX6150's "FastLane" feature. The first plot shows extended wireless throughput using the 2.4 GHz radio to connect back to the base router and the 5 GHz radio to connect to the extended test client. I suspect the instability shown is coming from the 2.4 GHz backhaul, since previous plots using 5 GHz radios only were nice and steady.
NETGEAR EX6150 extended throughput via FastLane w/ 2.4 GHz backhaul
Switching over to using 5 GHz backhaul provides higher net throughput in both cases, but not very stable connections. The big dropouts in 2.4 GHz link again indicates some unhappiness somethere in that chain.
NETGEAR EX6150 extended throughput via FastLane w/ 5 GHz backhaul
Seems to me the 2.4 GHz connection is the weak link in both FastLane configurations and overall for the EX6150.
The EX6150 earns a SmallNetBuilder Ranked #1 award, because it had the highest results in all ranked performance categories.
But given the EX6150's 2.4 GHz wonkiness, I'd also give Linksys' RE6700 a look. Although it doesn't produce the EX6150's higher 5 GHz throughput, its 2.4 GHz performance is as good or better. The RE6700 also provides a pass-through power outlet, CrossBand technology that supports simultaneous opposite-band backhaul on both bands and DLNA audio streaming.