Lunar, the drive itself is the important part. The rest of the package is just a box with disposable electronics in it, readily replacable.
Pre-made external drives are either (a) a rip-off way of selling a perfectly ordinary, stock-standard external box, and a perfectly ordinary, stock-standard 3.5 inch hard drive, or (b) a rip-off way of packaging a non-standard and difficult-to-repair or replace external box with no practical advantages over a proper standard unit, and a perfectly ordinary, stock-standard 3.5 inch hard drive.
Buy whatever external boxes you like. In them, put the best, most reliable drives you can buy. This means Samsung. First, last, and always.
(Er, that's "always until further notice". If Samsung start shipping drives of lesser quality than has been their habit over the last five years or so, I'll let you know. Meanwhile, they are not just the best, but the best by quite a margin. There is no choice. Samsung is the answer.) (Well, I'd consider a Hitachi if pressed to it. But not if I could buy Samsung.)