Difference between the two Save As .docx choices

What are the differences between Save as type: Microsoft Word 2007/2010 XML (.docx) and Office Open XML (.docx)?

Microsoft Word does not implement their own format Office Open XML correctly, which causes compatibility issues. Therefore LibO has two different file save types, one which is compatible with MS Word, the other which does things as the standard says, therefore the “correct way”.

To send files to your colleagues who use MS Word, you probably should go with MS Word 97 doc (docx export is not that brilliant yet). For any other use you are better off with odt format.

Microsoft Word has two Save As options as well, Word Document (.docx) and Strict Open XML Document (.docx). Are these the same as LibreOffice’s options? Should the second .docx choices be fully compatible? Here’s a pic of MS’s Save As.