The link in my first post has a good explanation... It is worth reading I think.
I had already read those pages but there are technical terms I don't know/understand (API? In my zone API are bees. ).
I thought Regedit was a distinctive program.
API = Application Programmer Interface
The OS provides function calls for the application programmer to do stuff, like open files, change screen mode etc..
Other than this utility I've seen other write-ups why Regedit methods aren't that great to use. Also the fact that I tried exporting and importing using it and it never worked as expected.
But the main reason to use Shadow Copy is so that the files do not get corrupted. Once the snapshot is made processes writing to the Registry do not alter the files in the snapshot. It's the same mechanism used by some of the Sandbox programs like ToolWiz TimeFreeze. Programs or viruses that think they are writing to C: partition are really writing to a cache file on C: set up by the TimeFreeze program. It is virtualized.
Regedit is better than using nothing. But I like the Shadow Copy approach. Even though it is dated ERUNT still provides some backup. But it doesn't cost anything to use Shadow Copy. It just does a better job.