wifi will most probably decrease ur network ping due to signal propagation delay.as far as increasing speed is concerned,many people claim that by directly connecting the DSL modem wire to the console,u will get better speed and pings but i use a network switch in my home and my speed and ping is perfectly ok.in some cases itz evn better than other people using the direct connection!!!
i think as long as ur network is distortion free and not shared by many systems at a time,u will be getting maximum out of ur connection