You've written for both manga and mainstream comics.
How is scripting different for those two formats?
Also, when I script for mainstream comics, I often include detailed descriptions of backgrounds and setting, while in manga, typically there's not as much detail in those areas, so I have to focus more on the action and the faces and body language of the characters.
Also, dialog -- I can get away with overdoing it sometimes in mainstream comics (but not all the time). However, in manga, less isn't just more, less is all you get.
Those are just a few things off the top of my head. Remember, though, as I write more manga, I'll learn more and some of these may change.
ADDENDUM: My friend, the manga artist Steven Cummings, has correctly identified the criteria I put forth as being more specifically for a certain type of manga called Shojo, which is most most common type found here in the U.S., and the type I'm most familiar with. (See, I'm learning already.)