well I bought all 3 of the big ones listed here and they all have thier merits. I like Birnbaums for the lovely colour pictures, but thats about it, gives you a nice feel for disney though. i would then read the Unofficial Guide to get a good touring philosophy going, and pick up all my need to know hints and tips, they really know what they're talking about. lastly I would put all that info together in a plan into my Passporter. I also like the reviews given in Passporter, so a combo of all 3 books works well for me. If I had to buy one, it would be Unofficial Guide.
Sorry for the rambling,
Claire xx