There are very few HDD manufacturers in the world. Of all the brand names, most of them come out of the same 3 or 4 factories. This caused a problem a few years ago when one of the factories was flooded.
It's important to remember that Buffalo don't make hard drives. They make the boxes and interfaces. The point of having raid in a backup device is specifically to cover for HDD failure.
The Buffalo NAS boxes are easy to use. Go for it.