All packages include both editions of the eBook, but if you want to get a physical copy (and only one), and can't decide which is best, ask yourself one questions:
Do I ultimately want to be able to read and write Japanese?
If so, the Kana + Kanji Edition will probably be better in the long run. It will likely be more challenging at the beginning, especially if you are not yet familiar with hiragana, but as you progress through the book and your reading skills improve, the Kana + Kanji Edition will actually become easier to read. Plus, you always have the Romaji Edition eBook to fall back on if it becomes a bit too much while you're still getting used to the characters.
If, however, you are mainly only interested in learning to speak and understand spoken Japanese, the Romaji Edition will be much easier to work with as you will have one less (very large) obstacle in your way.