Thank you for the detailes answer, this is the kind of thinking I was looking for. Because our assemblies are very simple and with no more than 30-40 parts each (at a great maximum), I think I will stick with the Inventor format. As other have pointed out, it is always possible to batch convert these files later.
What about emedded data in idw vs dwg files when cycled between AutoCAD and Inventor? Specifically, is data entered in iproperties within Inventor editable in AutoCAD, and is data entered in attributes within AutoCAD editable in Inventor? When an idw file is saved as an AutoCAD file, what happens to the iproperty data? One example: Data stored in a title block from an idw saved as a dwg file file isn't easily editable via a dialog box from within AutoCAD, if it is editable at all.