Your wireless game controller probably contributes more to latency than your in home network. Your television almost certainly does.
That said, latency is additive since it all happens in serial, and if the sum of it hits a certain threshold ("human perception") you begin to notice. So maybe you save a few ms from the network with wired vs wireless, or a few ms with a fancy "gamer" controller, or a few ms with a nice gpu-powered video encoding algorithm.
Shave enough of these things (which are only now being designed with this sort of over-engineered latency in mind), and eventually playing over the network is less latency-prone than playing directly on a machine from not that long ago.
That said, latency is additive since it all happens in serial, and if the sum of it hits a certain threshold ("human perception") you begin to notice. So maybe you save a few ms from the network with wired vs wireless, or a few ms with a fancy "gamer" controller, or a few ms with a nice gpu-powered video encoding algorithm.
Shave enough of these things (which are only now being designed with this sort of over-engineered latency in mind), and eventually playing over the network is less latency-prone than playing directly on a machine from not that long ago.