Find the differences in two Huge folders on a windows 10 system.

The best I can describe the problem: Folder B should be an exact duplicate of Folder A. But a check of each shows that B is about .3 TB larger than A. One is 1.43 TB the other 1.73 TB. I need a way to quickly find out why. Both A and B contain the same number of 2nd level folders so it is something deeper. Until I know what, it is possible that B has some files or folders that need to be added to A. I don't want to use an automated process that would make that choice for me
A program that could quickly list Only the folders that don't match showing files and folder sizes would be perfect. Does anyone have any suggestions? I know I have seen many over the years but none come to mind right away.

Argh!
Command-line options ! Why didn't i think of the easy way I'm getting lazy in my years.
i think i was hoping for a program that once it found the differences i could choose what to do with them from within the program. .3 TB is going to be a lot of moving something somewhere. The other possibility is that the files themselves might be duplicates. Whether dupes as in x.x(1) x.x(2) or otherwise i will wait to see.
FC will show me what is in B that isn't in A. I agree and technically that is all i asked for. :)
Thanks

PS: Got a nice chuckle out of your tagline ..but not for the reason you might think :)
I assume your reference is to as seen in that book?

PPS: I forgot! Last time i tried to pull a dir of a folder containing hundreds of thousands of files to txt the file was HUGE! and took forever to create. It was so large it took a LONG time to open (or NEVER) in Notepad, Have to resort to other text editors of which i have a few. But you said DAT:

Total Commander's Synchronize Directories is also a good option. You can even compared by contents.

FreeFileSync will do the job.