I love and adore reading. I'm not sure I could live without it. For me it depends on the plot of the story and which one interests me more.
I have to say that novels and mangas have both have their own advantages. Novels are very detailed and they challenge you to come up with what the characters look like. Some can leave you in such suspense that you have to keep turning the pages to see what happens.
Mangas bring a story more to life because you can actually see the characters and you can see the emotions on their faces instead of having to imagine them and that can cause more impact. Mangas can also power your imagination so it can help you read novels. I know that before I started reading manga that while reading a novel I could visualize scenes in my head just fine. When I started reading manga though it seemed that the characters and scenes that I would visualize in my head had come to life even more. Almost like watching a movie.
So it's a thumbs up for both of them in my opinion.