Whoa there, back up a second. What type of connection are you referring to? Internet? Copying files between computers on your home network?
The fastest Ethernet for home LAN is GigE, or 1000Mbit/s (theoretical). This will beat any WiFi connection hands-down, since 802.11n only goes up to 300Mbit/s (again, theoretical). But Ethernet will be limited by the lowest common denominator, thus if you have a GigE LAN card but only a 100Mbit/s switch, your entire LAN will operate at 100Mbit/s maximum.