There are only few differences, like the left/right paragraph margin is called left/right in one version, while the other version calls them start/end. In general, if you want to interact with Word, the “Microsoft Word 2007/2010 XML” version is the recommended one, when the OOXML standard and Word behavior conflicts, this filter will give you the Word version. The “Office Open XML” one will give you what the standard specifies: this is still understood by newer Word version, but not e.g. by Word 2007.
It is not an accident that “Microsoft Word 2007/2010 XML” is what gets selected, if you type “.docx” in the save as dialog and it sets the filter type for you automatically.