Actually, on average, WiFi will make your connection and ping considerably worse. WiFi, since it's not a hardwired connection, works harder and takes longer to transport memory and keep a stable connection, thus causing your bandwith usage to skyrocket. However, like any other internet connection, the closer to the source of your connection, the better your ping (as in lower). So, with that said, I strongly suggest using hardwire ethernet/broadband. Quicker connections, more stable, and your average ping (in regards to gaming) will be less of that than WiFi.
I'm sure your reasons for WiFi are fair, but as I said, I suggest hardwire.