The Deskstar 7K4000 is the performance-oriented model with 7200 RPM and a 64MB cache, while the Deskstar 5K4000 drive focuses on power efficiency and quiet operation. Downloadable software allows allows 32- and 64-bit versions of Windows, OS X and Linux to access the drive as a single volume.
Both drives feature a 6Gb/s SATA interface. The Deskstar 7K4000 costs $399.99, and the Deskstar 5K4000 drive will ship in 2Q12 for $379.99.
If you need an external drive, Hitachi has another two options. The Touro Desk USB 3.0 external drive is now available in a 4TB version for $319 (using the Deskstar 5K4000) in addition to the 1TB, 2TB and 3TB models. Yes, that is cheaper than the internal model - go figure.
And there's the 1TB Touro Mobile UCB 3.0 bus-powered external drive, due to ship next month at $159. It joins the existing 500GB and 750GB models.
Hitachi GST is in the proces of being acquired by Western Digital. The deal is expected to close next month.