Creating Scratch layer gives me a choice between Polygon and Multipolygon, so I started wondering how should I make use of them.

[![New Temp Scratch Layer][1]][1]

Reading a new book *"Mastering QGIS"* (through [this answer](http://gis.stackexchange.com/questions/220894/what-does-buffer-mean-in-the-qgis-voronoi-dialog) by Joseph), authors' comment was `"ESRI shapefiles store geospatial data in multi- type geometry, so using multi- type geometry is a good practice if you plan on converting between formats."`

How should I choose one of them (Polygon or Multipolygon) when I create a new polygon layer?
(I had confused multi-polygon with multipart-polygon, so I used to choose Polygon.)    

[Edit] One recent situation I have come to choose Polygon/Multipolygon was [this question](http://gis.stackexchange.com/questions/225297/parallel-line-length) in which I draw a dummy polygon as a background layer. Working mainly on shapefiles it seemed I was supposed to choose Multipolygon, although I needed only one polygon. In this case what I needed was simple polygon geometry without any attribute (Not sure this example make any distinction.)

  [1]: https://i.sstatic.net/D4ra0.png