Nintendo Wi-Fi is free, but the Xbox has better connection(I dont have an Xbox but I could tell by looking at some online plays on youtube). You can get internet on the Wii, so you can play any flash games that don't need a keyboard that you want. I doubt you can play games that require a keyboard on Xbox and PSN too. So they all have the same features, Xbox has better speed, but is not free, so they tie.
Any of you that put one above the other are obviously fanboys. It's better to know the thing you are rejecting than to just reject it.
I don't know about playstation network but even as a wii fan i HATE their user interface! the whole 10 number code thing has no point and doesn't even do a good job of protecting younger users. You can go on any chat website and exchange friend codes! xbox all the way man!