Better than the other - this one can delete permanently! Rated 5 out of 5 stars
I have used this as well as the other "Remove Duplicates" and like this much better.
The other one does not have the option to permanently delete the dupes. When I would find messages in the Trash, I was often not sure whether they had been deleted intentionally. To be sure, I had to waste time moving them back to the original folder and de-duping again, then deleting them from the Trash.
With this extension, I simply choose to delete them permanently the first time and I need never wonder about that.