What are the differences between MyFilms and Moving Pictures plugins for MediaPortal?
The main difference is that MyFilms focuses on the database/catalog, and advanced database management. It supports, or creates, a standalone (end-user) database which allows you total control of your data and artwork, and supports almost any configuration or method of storing your media, anywhere you wish. MyFilms also offers many of the advanced features of movie catalog software within the MyFilms GUI.
Moving Pictures is designed to make your media available in MediaPortal as easily as possible. The database is used primarily for this purpose. It does not offer a standalone database or all the features that come with it.
Thus, although both plugins offer a similar interface with MediaPortal, they use almost entirely opposite methods. You should choose the plugin that best matches your needs.
For further info, see the discussion in the MediaPortal Forum: Differences between MyFilms 5 and MovingPictures.