Omega has a lot more pages and it is a lot more "balanced" having good details both on maps, fiends, characters and story.

Battle Ultimania has a picture of each weapon, and battle strategies and goes into a deep discussion of Gambits and the license board. Maps are less detailed.

Scenario rules on maps, story and character descriptions. It goes into tons of details on those and just gives the basic on the rest.

IMHO, if I had to buy only one it would be the Omega Ultimania.

I have all 3 so if you have more questions ask away or look at my wiki
http://ffproject.net/forumwiki/index...chandise/FFXII