Ditto adds nice consistency if you're running multiple stage 1s, like for instance zoropod or zororoc. Most of the time the basic itself is better as they usually have more hp and an attack. Nice if you want to run 5 basics for consistency, or for just being a universal basic that can become any stage 1 in your deck and surprise the opponent. This even means we can run some surprise stage 1 techs more consistently.
Kahilis interesting, but really bad. Drawing 2 cards off a supporter is only good when paired with another effect, like kukui. This is purely a draw supporter and it doesn't do its job very well.