There are basically two external enclosures most folks use in the United States. Europe has "Icy Box" of which I know little about, other than I'm sure it conforms to their AC power requirements.
1. Vantec NexStar DX (NST-536S3-BK)
2. OWC Mercury Pro
The Vantec is black, one side is curved, meant to be used vertically, I guess, looking at the picture. These are lower quality than the OWC in my opinion and from experience with dozens of them. The circuit board has been DOA on several that we narrowed down to a bad batch. there's nothing to that circuit board to have something that simple go bad, or be missed in QA, that's a problem in my book.
Fry's took it off the shelf and made it a custom order item. I said WTF and last night was delighted to find 5 on the shelf which all came home with me. I believe the circuit board issue is fixed and should no longer be an issue. The overall quality issue of things not lining up perfectly and uneven gaps on either side of the drive once installed, those remain, and can be tweaked. If black is your color then this unit is for you.
OWC is white or beige I suppose. I feel it's higher quality than the Vantec, it goes together easier, spacing looks good after final assembly. Meant to lay flat, it looks like something Apple would sell and is usually the choice of Mac users. If white is your color, or you'd prefer to run your drive horizontal, this is your unit.
Price difference between the two is negligible, below ten dollars, who cares. If Fry's had these on the shelf I'd buy them all every time they restocked. They don't. I use Mac Sales or Amazon if it's super time critical but I'm going to stop with that Amazon. Too many brick and mortar places are going under because of them. (Keep in mine this is all MY OPINION and not meant to start a debate).
I don't remember off the top of my head if the speed of using the drive in an external enclosure over USB 3.0 matches the speed of a direct SATA port connection. I believe direct SATA will be faster but not sure of how much. I can test this a little later.
Anyways, that's my take on the external enclosure discussion.