Lol you have to read the manga and watch the anime and see the two versions. The manga shows a more normal life for all the characters while the anime rushes everything to awesome battles. So which do you find better?
Haven't read the manga? You should! Lol Black Knights doesn't just start out right out of the blue. Lulu is stuck only with Kallen at the beginning.
Code Geass: Lelouch of Revenge.
Code Geass: Suzaku of Counter Attack
Code Geass: Nunnally of Nightmare
The first and the second version is similar to the anime version, but Nunnally's version is the real original one, even Lelouch is rumored Dead in her story.
I believe a particular volume of the manga, most probably, that of Lelouch's storyline, was separated into "for boys" and "for girls" only. Since the manga was wrapped up, I am unable to tell if there is any difference in its storyline, though both covers most certainly appear to be marketed at each gender. :D
anime for sure
simply because the series has started with the anime, while manga adaptations as well as spin-offs were introduced later. hence, the anime is the original source of the plot and should be considered as the "real" code geass, whereas the manga adaptation only reflects the anime by a certain degree (britannian / eleven school? suzaku already at ashford at the beginning? Lloyd SMOKING?). btw: action based plot > commoner life based plot o0
besides, i like the drawing style from the anime much more, as the manga versions aren't CLAMPlike enough :P
Nightmare of Nunnally is pretty interesting. (Hurry up and start printing those manga Bandai!) I haven't read Suzaku of the Counterattack, but I have read some Lelouch of the Rebellion. None of the manga have exceptional art, so the anime wins there, and the Lelouch manga feels 'watered-down'. No Eleven massacres there and Kallen isn't a terrorist, she's merely a delinquent!