Wow, I barely understood the original post. Reason I say that is, "wireless USB"????
If you mean, do you need a USB WiFi adapter, NO. The Wii has WiFi built in. The Nintendo WiFi plug is only needed for DS owners who don't have a WiFi home router/access point (like a Linksys WRT54, or Dlink's models, etc.)
I clarify this because I hear people talking all the time about how one has to buy the Nintendo USB WiFi adapter to get the Wii on the net wirelessly. I've had five people argue with me that I'm wrong and that I can't be on the net since I didn't buy one. So, don't buy a USB WiFi adapter (plug, dongle, whatever you want to call it).
In general, WiFi (B/G) is not as fast as wired-LAN. Only if you are running wired 10mb and WiFi-G would your wireless be faster than your LAN.
However, broadband is no where near as fast as WiFi-B and only if you're lucky is it 1/10 the speed of WiFi-G. There are a few inexpensive Wii USB ethernet adapters on the net. Last I saw they were around $20us.
Wired Ethernet: 10/100/1000mbps
DSL: 128kbps-3000kbps (3mbps)
cable: 512kbps-8000kbps (8mbps)
Sat: typically less than 1mbps