Instead of simply allowing waypoint-by-waypoint navigation, the CNX-80 / GNS-480 is a Flight Management System (FMS). The primary advantage is the ability to selects Victor airways as a whole, rather than enter each of the waypoints which define the airway.  This greatly simplifies the creation of flight plans.  Perhaps more importantly, this makes it faster and easier to change the flight plan on the fly when given changes by ATC.

The two best features of the CNX-80 / GNS-480 are the opening of thousands of runways to precision WAAS GPS approaches, and the ability to provide a WAAS position fix for an ADS-B solution.