AllSync & AllDup

I have been using a similar program, which allows the searches to be saved in a checksum database. Thus I can compare duplicates in a folder versus saved searches.
Furthermore, an option is to find duplicates based on checksums. I assume that this would be faster than a byte-by-byte comparison (as in in Alldup)?

Addition of these two features: checksum database and comparison by checksums would be great!

creating and using checksums to detect duplicate files is only faster if no duplicates files are found or you have large files and all have the same size and only at the file end is a little difference...under normal circumstances byte by byte is faster.

What about using a checksums database to save previous searches?
In this way I can use previous searches, e.g. from a previously connected hard drive, to compare against a current folder/hard drive. Very useful!