Ok, so I've been running multiple tests with ping <adres> -n 500.
Just to be clear, this is my exact home setup.
Cable modem going to the router (Asus RT-AC66U) with a Cat 5e cable of about 15 meters, unshielded.
The router is set up as my private AP, no one else has acces to it and I disabled all my other clients except for my laptop (Alienware M17x R4, with a Intel AC 7260, it's running on Windows 7 and Bluetooth has been disabled trough the taskbar), there is only one LAN port in use, which feeds into a Netgear Prosafe GS105 (5 port Gbit switch with a total throughput of 10 Gbit if I may believe the spec sheet, induced ping at Gbit specs should be max 2 ms).
All ports of the switch are occupied, with 3 feeding directly into other pc's (my Alienware, a Acer laptop I use as remote device and a desktop which is off at the moment), all these clients have Gbit ports. The 5th port goes into another switch towards the rest of the network, but since no traffic is going there for the test it is irrelevant.
My first tests were to google.nl (me being dutch, the .nl domain should be closer than .com)
5.0 Ghz: minimum 12 ms, max 28 ms, average 15 ms.
Somewhat of a bumpy ride, but + 25 ms occurrences were rare
2.4 Ghz: minimum 12 mz, max 62 ms, average 16 ms.
rather bumpy ride, with quite some 35 ms occurrences and rarely higher than 36.
One packet out of 500 was lost.
LAN: minimum 11 ms, max 26, average 13 ms.
Also not perfect, but it was really rare to see a bump above 25 ms, closest to 5 Ghz in my opinion.
Whilst testing with a LAN cable I imagined there were too many variables, namely the modem, the ISP and the WAN to LAN link in the router itself.
Since the Acer laptop is basically doing nothing I decided to ping that 500 times trough the LAN, since only the Netgear switch isn't being utilized to the max it should have enough room not to be too much of a hurdle during the test.
LAN: minimum 0 ms, maximum 7 ms, average 1 ms.
Some bumps every now and then, but usually only 1 or 2 ms (probably something trying to access the internet for a moment on the Alienware or the Acer I suppose), one odd 7 ms spike and some 3 or 4 ms ones.
2.4 Ghz: minimum 1 ms, maximum 65 ms, average 2 ms.
Not even that much of a bumpy ride, mostly 1 ms responses with 2 ms also appearing a lot. Some bumps of 3 to 5 ms, but I guess that's just WiFi.
There were regular 12 to 25 ms bumps though quite some time within close proximity of each other and a small number of 35 to 60 ms ones.
It is not something I'd prefer to game on :/
5.0 Ghz: minimum 1 ms, maximum 259 ms, average 2 ms.
Other than the massive spike it was rather stable, only a tad behind the LAN connection.
The spike was odd though, it was a ping of 125, followed by a 44 one, 1 and the 259 ms one. it was the only time it came above 2 ms :s
To complete it I've also tested how the router influences it all.
LAN: minimum 1 ms, maximum 10 ms, average 1 ms.
Quite similar to the LAN connection to the Acer laptop, with it losing probably only 0.5 ms due to the switch and the LAN connection of the router itself, nothing spectacular really.
5.0 Ghz: minimum 1 ms, maximum 10 ms, average 1 ms.
Nearly identical to LAN, lost one package out of 500 though and one spike of 3 ms other than the 10 ms one.
Odd that there wasn't a massive spike like the previous 5.0 Ghz test :s
2.4 Ghz: minimum 1 ms, maximum 234 ms, average 3 ms.
Regular spikes of 10+ ms with quite a number of 25+ ones, I seem to have missed the 234 ms one though :/
My guess would be that there is quite some lag induced in the WiFi to LAN/WAN transition which amplifies the spikes.
5.0 Ghz seems to be working rather fine as far as my setup goes, aside from the odd spike in the second 5.0 Ghz test.
2.4 Ghz is riddled with spikes for some reason. I don't think most would be noticed during normal internet usage, but during gaming I suspect you could certainly notice them.
At the end I've quickly checked the spot I'm sitting at with WiFi analyser ( on a HTC one M7 with the latest updates) and the channel I'm using seems to be clear of other AP's (reinforced concrete walls help somewhat with this and manually setting the AP channels).
The AC's driver is 17.1.0.19 btw.
Ps.
@Intel people.
If you want/need me to test something else give me a PM.