Wifi will perform at the same speed as if you were on a wired connection, or that your ISP provides you with, and assuming your router is capable of handle those speeds. The only drawback though is signal strength, wired will experience little to no packet loss due to signal strength because the signal is contained within a cable as opposed to wireless which is susceptible to signal issues if walls or obstacles are within line of sight. And with wired or wireless, the more devices you connect, the slower your internet will get since it is distributed to everything connected to it, unless configured otherwise for QoS or something like that.