Well, on the positive side, none of them are exclusive; you can learn them all, and knowing one will likely assist you in understanding the other two.

IMO, assuming you're starting basically from scratch, you should start with the CWNA, then Cisco, then the Airmagnet course, if you feel you need it at the time.

My rational is this: The Planet3 books and course materials are excellent (they also have Professional and Security ... CWAP and CWSP which includes education for using wireless 'sniffers').

If you begin there, you will learn the fundememtal and foundational concepts, and have some good references.

Following that with Cisco wireless training will permit you to build on the foundational concepts ans show you how Cisco adapted / adopted the concepts to implement their product, and the scope of applications appropriate for their product offering.

By the time you've completed the above courses, you should have a pretty solid understanding of the technologies, protocols, and nuts& bolts ...

At that point, you may find the CWSP and / or CWNP training more useful, they show you many of the various tools and software used for wireless diagnostics and security management and in-depth understanding of the protocols.

The Airmagnet training is probably useful (I haven't seen it, got it, or read about it), depending on the content: Does it cover interpretation, or just a "how to use" and description of features?

My point is that until you understand the underlying protocols and technologies, a tool that requires interpretation of the results will do you no good. Even if the device has "expert software" to assist with the interpretation, it doesn't cover everything, and you'd have no basis to understand if the presented interpretation by the expert software seems "reasonable."

Good Luck

Scott