The nice thing about the Seagate GoFlex drives is that you can add TB if you choose. You can buy a USB or FW800 drive now... and upgrade to TB in the future if your needs demand TB.
For example: My 2009 iMac does not have TB... but I can use a USB2.0/FW800 drive which performs quite well if using FW800.
If I want to use the same drive on my MBA, i am limited to USB 2.0 which is much slower. However, if it is a Seagate GoFlexI can buy a $99 TB adapter and get fast speeds with with the MBA using TB.
So far, I have a Pegasus 8TB R4, Seagate Desk GoFlex with USB2.0/FW800/TB, and a Seagate portable GoFlex with USB3.0/TB. The advantage of TB for the Pegasus is obvious. I think I will use it to house my A3 library because it just screams. With my old iMac, I now use FW800. For my MBA, I connect through a ATD, and daisy chain TB drives. The MBA feels very fast with an internal SSD, external RAID, and a high res ATD monitor.
/Jim