[Milhouse]

Why would I not want to use local files?

Because if you enable "Use local files" Artwork Downloader will create files called disc.png, and your reference to "Titanic-discart.png" made me think you were using the movie-name prefix naming convention which is not compatible with Artwork Downloader.

Typically users will use the movie-name prefix file naming convention when they have multiple movies in a single folder. In this situation, Artwork Downloader with "Use local files" enabled will create a file called "disc.png" and then associate this same file with every movie in the same folder, which is usually a bit of a disaster.

On the other hand, if you are storing single movies in their own folders, then creating files with the name "disc.png" is not a problem, although this may still not be what you expect if your local files are called "Titanic-discart.png" (or whatever).

Then if something happens to my database I don't have to do anything but quickly re-scrape everything again.

You'll still need to run AD to scrape the non-standard artwork (disc, clearart etc.) into your library.

And if you're using the movie-name prefix convention - I don't recall what convention the Library Export creates, is it movie-name prefix or not? - then AD will not help you as it doesn't support that naming convention. If you were to enable "Use local files" expecting it to find your movie-name prefix files, AD would instead dump new "simple" - ie. disc.png - named files into your file system and library, leaving you with duplicate artwork files.