The following is from the M$ converter page:

The following issues might occur in this Beta release:

Graphics and other objects in the document might appear with a different size.
Color fills and shading in tables might not be preserved.
Conversion might not succeed if the document contains a bibliography or citations.
Conversion might not succeed if the document contains WordArt.
Document layout and formatting might not be preserved.
Some Unicode characters might not be preserved.
Conversion might not succeed if the document contains very large pictures.
Conversion might not succeed if you use an SMB network volume as the preferred destination for converted files.
Picture bullets might not be preserved.
Fonts might be substituted.

So, IMHO docXconverter does a better job.