Can you explain this senctence to me:
The top antenna pictured is considered a co-linear antenna or phased array with a theoretical gain of approx 2.1 to 2.4 dB over a 1/2 wave dipole or 5.1 to 5.4 dB gain over an isotropic radiator.
I do not know how to explain this any differently than stated.
My understanding of the antenna for the RT-N66U, you have pictured, is that the 2 sections are radiating in phase with each other. Which narrows their beam width and increase their gain. It is the same length but not the same design as a dipole. The depiction of the radiation patterns , though not 100% correct, are a good depiction of the difference or of what to expect each of them to be.
The side lobes are not shown but this might be a better depiction of width vs gain in single antenna radiation patterns.
The lag problem you are having with the time it takes for a page to start loading is probably Packet Loss. Even though you are connected at a faster rate it is trading off thyroughput with one AP versus reliability from the other. That wait time tells me the DNS lookup for the web site is failing at the faster connection speed. When the phone isn;'t getting a response to the lookup , it waits. When it waits long enough it times out and tries again. It might have to wait for it a few times before giving up, or finally getting a response. Do you want the pages to load faster once they finally start ? or would you rather they start loading immediately and finish before the other one gives a reply to the dns query ?
At your test location, if you are getting -81 dBm with the co-linear antennas and only -87 with the dipoles, the co-linear antennas are delivering 6 dBm better signal strength. That's what I would use.
I have no experience with the netgear router.
My download speeds usually match or slightly exceed what my provider advertises them to be. My ping times with my RT-N66U are in the range of 30ms to 40ms to most sites . Some may be slower due to network congestion and server load. So that measurement is relative.
To me, that I get pings or dns queries are answered immediately and not lose any is important. My router adds less than 1ms to the ping time when compared to a direct connection to the "modem".
The 2 bands are harmonically related . The 2.4 dipole will look like a center fed extended zep at 5GHz.