What is important perhaps for one or the other before, the My Book is a pure Apple product. The so-called Thunderbolt interface originates namely a collaboration between Intel and Apple and to the transfer of very large volumes of data enable (One can probably expand Windows systems to this port now, but since my knowledge ends).
RAID is a term for using multiple disks (in this case two). The numbers stand for the type of hard disk network. In a RAID 0 array, the data are quasi-simultaneously stored on two disks. But not twice. Now can be accessed in parallel to both plates to obtain a data set which increases the speed of data access.
In a RAID 1 system, the data is mirrored. Say the data are duplicated. This is the data security. If one disk on the system, you can replace it and restore the system. There is no loss of data, since they are left on the hard drive heal.
JBOD is ultimately the complicated form of expression to say, everything normal. With this setting, both plates are easily treated separately as individual disks / drives.
So what are the advantages of My Book and for whom it is suitable? Use only for the user very specific applications requiring very large and particularly high-speed data exchange. No Hobbyists needed in my eyes at these prices the advantages of Thunderbolt interface for everyday use. Only if you have to move fast data network, this acquisition makes sense. Say classic machining fields such as video editing and other graphics operations, where you have to rely on large amounts of data.
In addition, data security. By mirroring the disks obtained protection against the loss of data if a broken hard drive. Even if the data throughput then is slower than RAID 0, it is still significantly higher than in eg USB hard drives.
Hence my title, the My Book is intended for users who know exactly you want to use it what kind of applications. These are also no question mark at the key words and technical terms and also need not get these customers review.
Who cares as hobbyists for the My Book, can now perhaps better assess whether he really is the My Book needs, even though he really only an external hard drive seeks to save his holiday snaps.