I think a lot depends upon what you are looking for in a guide book. If you goal is to help get your friends excited about Disney and get them thinking about the fun things they want to do, Birnbaum's is a great book. If they are into maps and note taking, the Passporter may be best. And if they are obsessive planners, maybe you go with the Unofficial guide.
For what it's worth, I'm an obsessive planner and read every guidebook, every online site I could fine before going. Heck, I do this for every trip wherever I go. And I disliked the Unofficial Guide more than any guidebook I've ever read. I know tons of people love it, but when he described your child wanting to meet Mickey Mouse as an obstacle that needs to be overcome, I knew this book was not for me.