Hier mal die Antwort vom Support:
The nature of the .duf format is that it is universal. The old .daz scene format relied on reference files in the data folder. While this saved disk space it made the scene files very fragile. If the data folder was corrupted or any of the content moved locations the scenes would not open. In addition to this .daz scene files could only be opened on the computer it was saved on.
The .duf file format is larger because these problems were fixed. In order to fix these problems the file size had to increase. The majority of our users prefer a larger file size to limited functionality. In the days of hard drives that are orders of magnitude larger than they used to be and with cloud computing file size takes a back seat to functionality.