On iOS, Mangastorm works well for me. On Android, I've yet to find an equally capable app.

Hmm, I usually prefer the manga, mostly because I feel it's the real deal. A lot of times, we get a lot of watered-down crap or annoying extra characters/storylines in the anime. Still, for action-oriented anime, my imagination can only take me so far so I usually end up reading the manga then supplementing with anime. Also, I watch anime to fulfill my need to hear the characters' voices (rarely disappointed since the Jap voice acting is an art in itself)