One reason to upgrade is that the newer 60 series Garmin receivers can use Lithium primary batteries which was one reason I had considered upgrading. Then I switched to rechargable NiMH batteries and I see no reason to upgrade from an already great GPS.

One reason to upgrade is that the newer Garmin receivers such as the Garmin GPSMAP 64st use Russian GLONASS as well as the U.S. GPS system which may be a good capability. Don't know.