Seagate currently have their GoFlex external drives using the 1TB platter technology, but they feature 5400 RPM and are not as fast as the usual 7200 RPM drives. But, with 7200 RPM drives, there's usually less GB per platter. Seagate don't want this, and neither do we.
Seagate will now intro a bunch of new drives sporting the 7200 RPM spindle rate, with 1TB platters on a SATA 6Gbps interface. The new drives will have a model number ending in M00x which represents the new drive and its 7200 RPM speed.
Tech wise, platter capacity plays quite a big role in just how much storage a hard drive can hold, but it can also impact performance. Areal density is key, which is a measurement of how many bits are squeezed into each square inch. The more bits per square inch, the more data passes under the drive head with each revolution of the platter.