Hi Lumpy,
As with anything computer you get what you pay for. I like the pocket hardrives instead of the full size desktop drives. Quite often we see drives that have had the Laptop powersupply used instead of the 12volt powersupply supplied, which damages the drive and interface. So at least if you have a usb powered drive this isn't a problem
. USB3.0 is a must , and go for less capacity higher reliability like Western Digital My passport drives have served me well. Always the best idea is to have several copies of data so say 200 DVD's and two 500 gb harddrives are better than one 1tb drive.
Hope this is of some help
Lisa