Im in two minds about this, but ill say anime simply because there are somethings that can be better told through anime than through manga - e.g. Initial D, Great Teacher Onizuka, Beserk (i've forgotten what the manga was called) etc.
Well, there is a pseudo-superior 'counter-culture' within the anime/manga world that likes to claim 'Oh, manga is way better then anime,' because it's the 'sophistocated' thing to do.
The fact is, in many cases the anime is simply done better then it's manga equivalent--a major example would be Naruto. Naruto is a combat-based series, and the manga isn't able to pull off the fight scenes with style as the anime is. The majority of non-Japanese readers of the Naruto manga are doing it because the manga is further along in the story and they don't wish to wait for the anime episodes to slowly come out--and they're dissapointed they ruined parts of the story for the garbage manga.
i disagree with saying that the naruto anime was done better, it follows the manga almost word for word, and the only parts i found a bit weak in the anime, werent in the manga.... i understand what you mean about the fight scenes though, but it i think if you read it carefully instead you can understand whats going on and it still looks damn cool. With my shonen jump right next to me, the fights look awesome, (looking at the fight between kakashi and sasuke for the bells) its fluid, and very visually impressive. The naruto manga did an excellent job in communicating emmotion and you can really empathise with the characters, i found that when i watched the anime it was a little empty, for example, i hate the way Rock lee is portrayed in the anime, the music especially makes it worse, i thought he was a great character in the manga, but when i saw the anime, my opinion of him went down hill. I feel that the manga is better because it lets your imagination do more work, which imo, is better, it makes me feel more involved. Dont get me wrong though, the anime is good, i'd give it 8.5/10 but the manga i'd give 9/10....