Migrating from Aperture to Photos

You can delete the Aperture Vault.apvault, if you now are using a different backup for your Photos.

The file Aperture Library.migratedaplibrary is your current Aperture Library, just with a changed filename extension. If you change the extension back to Aperture Library.aplibrary, you can open it again in Aperture.

The Aperture library should have roughly the same size as the new Photos Library, but the two libraries are stored efficiently. All original image files are stored as hard links, so the storage is only used once. The identical files in both libraries are using the same disk blocks. You will not gain much storage, if you delete the Aperture Library. I would keep it around, until you have convinced yourself, that all photos are included and and you no longer need to look up metadata, that did not migrate well, like hierarchical keywords, descriptions of albums, faces names, location names. Then you can delete the file Aperture Library.migratedaplibrary.