An 802.11g laptop connected to an 802.11n router, for example, will network at the lower speeds of 'g' which maxes out at 20mb
Also, typical 802.11g Wireless has a theoretical maximum of 54Mbps. Typical wired 10/100 Ethernet has a theoretical maximum of 100 Mbps. So in theory wired is faster.
However, these speeds are only on your local network. Most high-speed internet connections range from 1Mbps to 25 Mbps. Even on faster internet connections you're only approaching 1/2 of the full throughput of your wireless system.
In practice, its not likely you will see much of a difference unless you are transferring very large amounts of data across your local network.
I typically make the wired/wireless decision based on the usage of the machine. If it is a desktop that will never move, wired is the way to go. If its a laptop that will be mobile, the convenience of wireless by far out weighs any difference in transmission speed.
If you’d like to know if Ethernet would be faster for you, try this simple test. Go to Speedtest.com and run the benchmark on your Wi-Fi-connected PC. Then, connect the computer via Ethernet (be sure to turn off Wi-Fi) and try the test again. If the second test is quicker, you are losing performance to the ether by using Wi-Fi.
Connections between home computers are a bit different. They rely only on your home network infrastructure, so the improved transfer speeds of Ethernet are always relevant. The question is, do you transfer large files between computers on your home network? If you do, Ethernet is still important; if not, Wi-Fi is just dandy.
Edited by chrisd87, 17 May 2013 - 10:18 AM.