10 years ago, LaCie was a popular goto vendor for Macintosh compatible hard drives. After a few of my Lacie d2's failed, I decided to try a different hard drive case and found some pleasant surprises. The Macally unit below is the one I chose.
Macally Hi-Speed eSATA/FireWire/USB 2.0 Storage Enclosure for 3.5-Inch SATA Hard Disk G-S350SUAB2 (Silver)
Priced at $65, this is attractive for a high performance Firewire 800/400, USB 2.0, and eSATA hard drive enclosure. Compared to my LaCie d2's, I noticed several improvements.
It's fan-less which makes it very quiet unless the disk is active.
I like that it includes both Firewire 800 and Firewire 400 on the back.
The power supply is a standard 12v wall wart instead of a separate dual voltage unit (12v and 5v) that sits on your floor or desk and uses a custom DIN connector. LaCie had a run of bad power supplies, so I like that the power supply is such a standard part.
The internal design is actually simpler than the d2 since the drive mounts horizontally and plugs directly into a controller card with interface jacks on the back. The aluminum casing is thinner but not insubstantial and much lighter weight. As an external enclosure, there's no issue with voiding the warranty by opening the case. In the LaCie d2, the drive mounts vertically and needs a ribbon cable (or daughter card) to run from the bottom of the drive to the controller with jacks at the back of the unit. A "warranty void if broken" label covers one of the screws you need to open the case.
By choosing a separate case, you can pick any specific hard drive (and warranty) you like instead of taking your chances with whatever the vendor has on hand.
I tried a NewerTech Voyager S2 USB drive dock for a while, but it wasn't reliable enough for Time Machine backups. Every few days it would report some file access error and need to be hot plugged. The Macally case with included Firewire 800 cable has been flawless for weeks (using the exact same hard drive).
As for bare drives, I've had good results with Hitachi drives ordered from OWC.
What About RAID and NAS
RAID (Redundant Array of Inexpensive Disks) and NAS (Network Attached Storage) get a lot of attention for business critical applications. In my opinion, these are not a good investment for home office or small business backup. In theory, RAID allows you to hot swap a failed drive without disrupting your storage array, while NAS can be used to backup several computers from a single convenient appliance. In practice, these are embedded computer systems (typically running Linux) with their own set of software compatibility and upgrade issues. When things go wrong, and they sometimes do, the added complexity makes it much more difficult to recover.
My preferred approach is to make sure any important data is backed up on at least two separate hard drives, with the most critical data also backed up off-site or in the cloud.
Drive capacities are growing so quickly that the current generation large capacity hard drive will often exceed the capacity of a drive array from only two years ago. Unless you need all that capacity on-line now, it's simpler and less expensive to buy a bigger drive any time you are running out of space. If you want the convenience of network attached storage, it's easier to configure an aging Mac as a storage server, than maintain a Linux based network appliance.
By investing in a flexible moderately priced drive case, you can simply upgrade your drive mechanism every few years, and deal directly with the drive manufacturer for any warranty issues.