One is 32k (Condor/2-digit models) and the other is 64k (Falcon/Newer 3-digit models). It allows more flash memory for the phone to access. The 64k is not supported in the older 2-digit phone models, however, the 32k is supported in the newer 3-digit models so long as all software updates have been applied [there were issues with the 1st round of Falcon software].