According to Android User Guide :
Image Asset Studio helps you create various types of icons at different densities and shows you exactly where they'll be placed in your project. It includes tools for adjusting your icons and adding backdrops, all while displaying the result in a preview pane, so they appear exactly as you intended.
Vector Asset Studio adds a vector graphic to the project as an XML file that describes the image. Maintaining one XML file can be easier than updating multiple raster graphics at various resolutions.