Document Library Vs Asset Library?

Asset Library is preconfigured to manage media content like images, audio and video files.
It has extra features over document library like Thumbnail view, Automatic metadata extraction for image files.
Document Library:

you can use it for sure to upload documents and use extra features that come with asset library.
Also you can add workflow and other features like versioning and everything that's possible in document library.
Only thing you need to do is to add new content types for Document and document set.