UDF has slightly more overhead in how it saves the filenames, directory structures, etc. But, it has much better support for larger directory trees, larger filenames, and a larger character set to use for directory/file names. There is nothing in either that affects data integrity - that is handled a layer below the file system with the ECC in each sector.
As a small test, I created image files of the same dozen files “burned to a cd” using each of the available file systems. The sizes of the images (in bytes) came out as follows:
ISO9660 stores the filenames in ASCII, no longer than 31 characters, and with no special characters.
Joliet stores the same ISO9660 driectory/file listings, but then completely duplicates the directory/file listing in Unicode allowing more than just english letters and special characters and allows for longer filenames.
UDF uses the same basic disk and volume layout, but uses a completely new and different layout in the directory listings allowing it to save information that relates to modern HDD file systems in order to save file ownership (uid, gid), access control lists, MAC times (instead of just a C time), and so on.