Mac Pro :: Backup Hard Drive Decision For Time Machine Only

I'd like to add a backup HD to my Mac Pro. Not with the intention of doing a RAID set up, but rather just for Time Machine. The two drives in my line of sight are the...

WD Caviar Green 1T
( http://www.wdc.com/en/products/products.asp?driveid=763 )
and the
Hitachi Desk Star 7K1000.C
( http://www.hitachigst.com/portal/sit...star/7K1000.C/ )

I know there's the Caviar Black, as well,, that has a 5 year warranty as opposed to each of the above's 3 year. But I hear its on the loud side, and since it won't be running much more than every other week I don't see the need for the added performance. But perhaps the 5 year warranty alone is worth it. I'm also aware that the Caviar Green will spin at 54K, and that Hitachi is at 72K. Again, the intent and purpose is to be that of a backup HD.

I have a friend that works in Google's server R&D department that swears by Hitachi (based on their excessive testing standards). But I have no experience with Hitachi. So I'm looking for a few more real world stories on what you all are currently experiencing. My main concern is which will be the least problematic over the long haul. I am not interested in Seagate's, nor Samsung's.