I prefer novels.
The reason is that with manga, I find myself trying to take in every detail on every single page, which makes reading them take a long time and leaves me exhausted—that just doesn't suit me. Since I've always loved reading text, I prefer novels.
Just one. The reason is that I like similar story worlds, and if I work on multiple ones at the same time, I'll end up mixing up which events belong to which story.
I listen for the story. I've always loved stories, so even if my favorite voice actor is doing the voice, if there's a flaw in the story, I just can't get into it anymore.
I prefer online manga to print versions. With print versions, I get upset when I accidentally get them dirty, and they just keep piling up, so I run out of space to store them.