It all depends on the quality of your router, the quality of your wifi adapter in your computer, how far the distance from your router to your wifi adapter, how many other wifi networks around in your area.
If all those factors are good, there is hardly any difference between wifi and wired.
Wifi is always worse then wired connection. It`s unstable even if the distance between router and computer is 2 meters. For gaming, internet - this is ok, but in mining this is losses. I calculated difference - it have been about 10%. Router was about 4 meters from rig
I have also tested this many times and I hardly see much of a difference. 10% sounds like a lot. What is the quality of your router and wifi, is it some cheap chinese junk? From what I can see there is less than 1% difference between wired and wifi.