Mahou Sensei Negima (the manga): Much, much more heavy on the fanservice. Heavy on the comedy and the fighting, and the plot is a lot more intricate.
Negima! (the first anime): Light-to-moderate on the fanservice, mid-range on comedy, heavy on the emotional moments and character development. Great BGM. Deviates significantly in its Gecko Ending, which some fans hate. Personally, I'd rank it in the top five series endings out of the few-hundred-or-so anime I've seen.
Negima!? (the second anime): Extreme on the comedy, wildly diverges from the plotline. Starts tame on the fanservice, but by the end it's right up there with Negima!, possibly beyond it. Lots and lots of Lampshade Hanging. The BGM is only okay, but the OP and ED are two of my absolute favorite iPod selections. (The Japanese OP and ED, that is. The Funimation English versions could make baby Jesus cry.)
The OVAs: A mixed bag. Earlier ones tend to capture the feel of the manga extremely well, even when they're not the same storyline. Later ones have the unfortunate tendency to try to cram a few dozen chapters in, but are visually awesome and follow the manga religiously. Fanservice varies, but tends to be a lot heavier than in Negima! or Negima!?
Negima!! (the live-action): Tried to watch it, but couldn't make it through the first few episodes. Bad acting, and too cheesy.
Recommendation: If the fanservice of Negima! or Negima!? really bothers you, you're safer not going any farther than those two. But if that's not an issue, and if you don't need One Plot To Rule Them All, watch / read everything (except the live-action) for the best experience. And get the soundtracks. (^_^)
Different != Bad.
Recommendation: If the fanservice of Negima! or Negima!? really bothers you, you're safer not going any farther than those two. But if that's not an issue, and if you don't need One Plot To Rule Them All, watch / read everything (except the live-action) for the best experience. And get the soundtracks. (^_^)