Even though many directories could have similar site structures, layouts and category options, each link received from these directories is an independent link. Each directory has a different editor and each editor will have different parameters to consider when reviewing and approving a site. Therefore, even if a site has been listed under the same category in different directories, there can be no two directories that will have the exact same links. Each directory is valued independently. Hence, it is definitely worth submitting to all, since each link coming from the directories would be counted as a separate and unique link.