One way to go - upgrade to the latest versions of iPhoto and Aperture. Both applications now share a unified library format. You could merge your iPhoto libraries and Aperture Libraries into one consolidated library on a dedicated external drive, and open these libraries either in Aperture or iPhoto, until you are sure, which of the apps is the right application for you:
(BTW: A similar approach will work to merge iPhoto Libraries into Aperture libraries).
- Upgrade your OS and your app versions to the most recent ones.
- Use Aperture, if you are comfortable with it.
- Consolidate everything in one Aperture Library.
- Create a top-level Folder called "Old Structure".
- Move all Projects into this Folder (in Aperture, every Image must be a Project).
- Select the Photos container. Sort by date. Look for dupes. Use the Info tab (or the Info tool tip metadata overlay) to compare dupes. Save the largest; delete the others.
- Identify your storage and your retrieval needs. Think on this. :-) .
- Add new Projects and Albums, and new Folders to organize them, to build a Library structure that meets your needs.
- Move Images and/or Projects from "Old Structure" to the new structure you are creating.
- Continue until there are no Images left in "Old Structure".
- Delete the Folder "Old Structure" and all its contents.
- Enjoy you newly organized photo collection.