Ethernet Cat6 Gigabit vs Wifi (Gaming)

Hey Guys!
I play a lot of online games, currently i have BT infinity (75 mbps) of which my iMac over Wifi gets about 60 mbps, my Hub is at the bottom of my stairs and my Mac in my bedroom, sometimes i experience terrible lag and as you can imagine on online shooters this causes a few issues. the back of the Hub has a gigabit ethernet slot and so does the back of my Mac so i put two and two together and figured i may as well run a 15m ethernet cable joining the two. However, not being a tech kid im not fully sure if this will help things a great deal. Will this reduce my Ping? Help fight off the lag and help my Mac receive my full 75 mbps?
Basically, will i actually gain anything from this?

That all depends on where the lag is occurring. If it's the wifi response, then yes, it'll be much improved. If not then there's no saying it will.

I game on my iMac, via bootcamp, over wifi and experience no discernible lag over an ethernet connection. So I know it's possible.

Ethernet cable is cheap but if you only have a short cable can I suggest just moving your Mac to the router temporarily and trying it first.