Different Word 2016 equation editors

[skan]

With the new Microsoft Word 2016 if you insert an equation through the Equation button within the Insert menu you get this new-looking editor.




Equations created in such a way can be viewed in inline, professional or linear mode and offer advanced options.

But if you use a keyboard shortcut (Alt+= or any user defined one) instead you end up getting this old-fashioned editor:


And if you edit equations from documents made by other people sometimes they are opened with the new editor, sometimes with the old one.

Can anyone explain the difference between them and how to force Word to always use the new one, please?, I would like to get it with a keyboard shortcut.
And also how to convert an equation made with the old editor onto the new format?

Regards