Well, I think different guidebooks are for different people. UG seems ideal for the ultra-planner, while something like Birnbaum's is good for someone who is looking for a more summarized version of WDW. Passporter is nice with all its print-outs and maps, so it is definitely best for a "hands-on" kind of person.
To me, UG seems like a novel with not many visual resources, no color, and extremely detailed and "commando" (not that there's anything wrong with it) descriptions and such.
I prefer Birnbaum's, but you get different responses from different people. A nice idea is to go to your local bookstore and just glimpse through the Disney guidebooks they offer and see which appeals to you best. They all contain mostly the same information. Any add. info can be supplemented by the DIS!