I have used a number of duplicate file removers over the years, and have found Duplicate File Remover is the most useful to me because of the "Merge Folder" feature. It not only finds files and folders that duplicates but also looks at folders that almost the same. Then File Find Remover suggests merging the two folders so that now you have the one copy of files in the one folder. I am not aware of any other duplicate file finding app that does this.
I have almost 2T of hard drive full of files I have accumulated over the years. A large part of this collection is made up of almost all the same files in different folders- a result of changing the way I manage them. I have been putting off trying to sort through these files and folders because of the sheer amount. I tried using file/folder sync apps to do most of the work, but could never work how to do it. So Duplicate File Finder has become a really useful tool to me.
Hats off to the developer for making this app and for pricing it so that it does not break the bank. Thank you! :)