The difference is the pcv has a built in hub which allows you to plug acessories directly into the unit without having to purchase a seperate hub.Auto tune box,quick shifter,lcd screen,wideband,etc can be plugged right into it. Also, it has a added 15% throttle position column where the pc3usb skips directly from 10% to 20%.The PCV is a better unit only because of its expandability,The tuning aspect is the same except for the added 15% column.:2thumbs: