Have to buy external HD for a friend's iMac. Any reason to buy one bigger than her internal drive?

[ka jowct]

Well. perhaps you could explain to her that the only difference she would see is a crummy 1-year warranty on the external you buy as such compared to 3 or 5 years on the drive that you install yourself in a good-quality case. Also mention that in some cases, she won't even know what drive she's getting, unless she buys an external Seagate or Western Digital.

Also mention that actual humans somewhere had to put the drives into those already-assembled external drives. Why trust them more than you?

She's just screwing herself if she insists on the pre-fab approach.