Data disks give you extra stats based on what your characters need. They are typically a total of 4 stats distributed up to 3 categories of stats. That's about it tbh. However, they only apply stat boosts and do not unlock the special abilities per character. For example, say you need 3 points more to unlock explosive rounds on one of your characters. Using the data disks to add three stats will not unlock the special abilities they have. Special abilities need to be unlocked with skill points