I would not really call UDF the 'Native' format for DVD's.
You simply have different File Structures used for differen purposes. Just as when working with Wood, you have differnet Files. They are all used for wood, but for different purposes.
ISO 9660 is the File structure most commonly used throughout all Computers. That goes for PC's, MAC's, etc. So most use that format to ensure compatibility between a large number of systems. However, the ISO file structure if very restrictive.
UDF is a more flexable allowing for larger file names and larger variety of characters. But not all systems have the needed drivers to read UDF file structures.
UDF/ISO is a combination of the two to give you the flexibility but still allow most systems to mount and read the disc.
You need to know who you are going to send the disc too and what they are able to read, or what you are going to create the disc for and what devices are to be used to read the disc. We give you the tools, you decide how to use them.