Well....I think both the methods would have the same level of complexity/simplicity.......but, overwriting the database doesnt really solve much of a purpose
Say you have your video files, and some music, radio (etc) in your WMP, with ratings, play counts, comments, tags etc in WMP. If I overwrite the database of WMP with the music of MM, the WMP with the new database would have all the music from MM, but lose the information of the videos, music, etc. that you already had in WMP, and obviously you definitely dont want that to happen.
If, we simply add information to the database of WMP, that would keep your WMP library and add the MM library.
Both of the methods require interpreting the WMP database language, thus the level of complexity would be the same.