Macworld:

Between migration and multiple imports and copying for particular purposes, you could have several copies of the same image or scene, and sometimes they aren’t identical: one may be lower resolution, one may have been edited, and some might taken in quick succession but only one is good! Burst mode can lead to a lot of extra pictures, depending on your settings.

Photosweeper 3 is a well-updated version of software designed to solve this problem with a high degree of customization and specificity.

I’ve used Photosweeper 3 to organize and/or delete thousands of photos. Well worth the $10.