Initially I only moved a few devices over to this network just to do some preliminary tests and check the range, but what I quickly noticed was that not only did this router provide a faster connection than my Portal router but also covered more range. With just the COVR-2600R up and running the range and speeds were pretty much a push with the Portal's performance. But after locating a suitable location for the COVR-1300E the range and speeds were much better at the other end of my house. And more reliable, sometimes with the Portal I would find that if two devices were streaming content I would get strange hang ups in the video. Originally I thought this was due to glitches in the app used to stream, but moving these devices over to the COVR's network seems to have eliminated this. Also worth noting; that was without using any QoS settings. So the difference is clearly signal strength and/or D-Link's Smart steering that actively moves devices between frequencies to ensure there is enough bandwidth to go around.
D-Link also claims to have Smart Roaming. While a few times I noticed my Moto G5 was on the extender even though I was closer to the router, I have to say there was no effect on performance. But I can confirm I could move from one end of the house (average 2500sq ft home) to the other and devices would maintain connection without having to change anything, it was seamless like a mesh network ought to be. And if you own a mansion you can purchase additional extenders to cover even more.
Surprisingly when I checked link speeds things didn't quite match up to my real world experience. As you can see in the chart below the Portal router was equal to or better than D-Link for AC devices.
I found this very surprising; especially since the speed in the master bedroom was done within 15 feet of the extender. I believe this is because the extender supports AC up to 866Mbps, but half of that is used to communicate back to the base, so only 433 is available. In this case the base unit has a stronger faster signal available and D-Link is using their proprietary Smart Roaming to make sure you get the fastest connection possible. Looking at the signal strengths confirms this; you will see two 5G networks for D-Link listed. The one with a MAC address starting with EC is the extender and has a signal strength of -63dBm and the other is the base unit with a signal of -73dBm. So even though the base units signal is weaker it is still a faster more reliable connection for the device.
Surprised as I was with the findings above I decided to take out an older device that didn't support AC just to see what kind of link speeds we saw. This is what really separated the D-Link from the Portal router. As you can see in the chart below, close to the routers there was no difference in link speeds. But once you started moving to the far end of the house on another floor the change was dramatic. Here you can see the benefit of the extender with a 3x link speed difference. Out by the pool which is about 100 feet from either the router or extender the difference was even more dramatic. Here I saw nearly an 11x link speed difference.
While I have no way to prove this, I believe my perceived improvement in streaming quality was due to the stronger performance for non AC devices. D-Link uses their proprietary Band Steering to move devices from the 5GHz band to the 2.4GHz band to minimize bottle necks due to over-crowding of the higher bandwidth 5GHz network. So I suspect some of these devices that would normally connect at 5GHz are pushed down to 2.4GHz since they can still maintain a strong signal and sufficient bandwidth. This frees up more bandwidth in the 5GHz band which in turn improves streaming performance.