In testing the difference between 802.11 G and N, there was a substantial difference between 802.11g vs 802.11n. Here are my results:

Results 802.11g Wireless USB 2.0:
Adapter Model: Cisco AM10
Ping: 11ms
Download: 2.96 Mbps
Upload 5.10 Mbps

With 802.11n Wireless USB 2.0 Adapter
Adapter Model: Rosewill RNX-N180USBE
Ping: 8ms
Download: 14.25 Mbps
Upload: 5.93 Mbps

Please keep in mind that your results may vary due to such factors as:
• Are you using a USB 2.0+ slot?
• Distance from router
• Signal Obstructions (physical or radio)
• Signal Strength

It is worthwhile to note my Cisco wireless adapter was fine in the days of "802.11g", but 802.11n reigns supreme now. Plus, my new wireless USB adapter has more power to it also (e.g. can go through my obstructions of walls to reach the router!!). Both models come with a USB base making positioning the antenna a viable means of signal control.

If your interested in purchasing the particular model I have, please use consider using this Amazon link: Rosewill USB 2.0 External 5dBi Antenna Wireless Adapter (RNX-N180UBE)

Since I worked for Comcast, I've been using Speedtest.net to test my connection speeds. It's free and very consistent. You can test your speeds before & after too. Please feel free to share your results!