but doesnt explain why its cheaper
It happened that I landed several time here while searching the same answer, so now that I have the answer, I'll write it here for future other people in searching for the same thing.
Seagate Freeagent GoFlex is newer.
Has Changeable Interfaces (USB 2.0, USB 3.0, eSATA, Firewire), instead of just USB 2.0.
Automatic Backup Software works in both PC and Mac, instead of PC only.
Slightly faster transfer rate.
Has 192-bit Triple DES instead of AES 128-bit encryption.