I have the same question...since 3 years. There is unfortunately no clear answer available.
The following represents my personal opinion and/or how I understood the topic. I am no PLM expert and I would be more than happy to get a better answer! (This is the main reason why I write this answer at all)
So what we see is that CAD and Document ItemTypes have their real strength when using them in combination with connectors. In this case Aras stores the native files and handle the document revision. This is the ideal situation and for this situation standard Aras is optimized. Aras assumes you will use it that way, so they do not have an answer for alternative use cases (prove me wrong my friends from the bay state :-) ).
When you do not use any connector, it doesn´t matter if you use the CAD or Document ItemType for storing your files. Despite a few properties and functions they are more or less equal. If you plan to use a CAD connector one day, it of course makes sense when you use the CAD ItemType from the start.
But now a provocative question:
When we do not use a connector, do we really need one of the two available Document ItemTypes at all? What is the practical benefit?
Benefit: When you use floating Documents in your Part you can exchange files easier without touching the Part revision.
Con: A Document ItemType without connector is just an empty shell for storing files. Much clicking for low benefits. And you might suddenly have three revisions for the same thing!
Let´s assume we have a drawing file called ‘bike_frame_2.3.dxf’. The dxf has a revision (2.3) assigned by the not connected CAD system. If we now upload this file to a new Aras Document, we will have an additional Document revision (e.g. A-2) and later an additional Part revision (e.g. B-4)!
What I have learned from the past: It´s hard to keep Document and external file revisions equal when using manual versioning. But stackholders will be confused by the number of available revisions, numbers and names.
So we have chosen an alternative approach:
We do not use any Document ItemType at all! We hid the Document and CAD tab in Parts and added an additional tab for ‘Files’. The files tab contains additional properties for revision and other information of interest. Minor File changes can be done by changing a hidden Part revision, that has no influence to the main part revision.
I would not say that this one is the best approach. But it simplifies at lot. It´s easy to use and more important: Easy to understand! And perhaps the most important point: We do not have to stick to this concept. If necessary, we can switch back to the original Doc-handling by adding the missing Documents Items and relinking the files. So from my POV it´s quite ok to start like this.
But that´s actually not the end of the story yet.
After some years situation has changed and we actually reactivated the Document ItemType, as we plan to use document connectors for certain documents.
But I right now use a modified Document ItemType that allows users to choose if the Document is authored by an connector or manually by the end-user.
The Document ItemType is mainly used for native files (e.g. docx) or internal documents. In contrary we use the Part Files tabs for documents, drawings or software files that shall be passed to external suppliers by a data package. These files may come from a Document Item (e.g. pdf converted from docx), but still can be added manually. It´s a very customer specific solutions, but it combines the best of both worlds.
I would be happy to hear your opinion!
I am more concerned with the CAD References. When I save an assembly, does it update references (children) of that assembly in a file reference table? Again, I don't have Aras installed, I a gleaning this from demos and conversations.
What I need: PDM Vaulting with where used and composed of at the CAD file level
What I dont' need: Integrated Aras menus embedded in our CAD Application (i.e. SolidWorks, SolidEdge, Inventor, ect)