Dont get either, get the Alfa AWUS036NH
It is hands down the most powerful consumer wifi antenna on the market if youre primarily connecting to wifi N/G/B.
I'm not endorsing any illegal activities, but alot of those who are into war-driving and cracking wep/wpa wifi networks use these Alfa cards because of the Realtek chips inside/compability w/ backtrack/aircrack etc.
but to answer your question, go with usb. it's more versatile/portable, and it wont take up a pci slot. You could also buy a usb extension cable and place the wifi card where it is more ideal, rather than be blocked behind your pc tower or up against the wall where the wifi signal is likely weaker.Edited by cozmo5050 - 1/30/11 at 9:41am