(Started writing this earlier, and I see now that @PaulWalters has done an informative post, with which I agree. But to continue what I started writing earlier:) I think this is mainly a matter of individual taste, but what I find is:
- I use outlines sparingly as organizing tools, mainly when there is a presentation I am preparing, or when there is some other obvious hierarchical categorization for the material I’m working with.
- I, personally, mainly use maps for scheduling purposes and/or whiteboard purposes – when moving things around, in a visible way, helps me understand them better.
- When I trying to organize research notes, data, writing information, and so on, I find myself relying very heavily on the Attribute Browser. That allows me to use tags and attributes of every sort to categorize notes, and then display them in whatever way I would like. Details and examples here.