Every hard drive is due to fail. All externals do is make it more "mobile"
Exactly why do you need it so high? Unless you backup full DVD movies, 320-500Gb is plenty.
But for Externals, I would go with Seagate, Western Digital, or Samsung.
For simple backups, the "slim" version (USB only) is ok.
For streaming movies or music, or just simply have it always on, I would reccomend one with external power.