Another difference is that WN's tend to be updated frequently but in small chunks (like a few sentences every day, or a few paragraphs every week), so the story telling style is usually pretty choppy compared to a LN.
Either way though, I almost always prefer manga to either WN/LNs. I've tried to read a few where the manga version is way behind the LN, but I just couldn't get into it. The translation in manga is mostly just dialog (were small grammar/style mistakes are understandable and easily forgiveable), and the drawings take care of all the background and context. Whereas in WN/LN, the whole thing needs to be translated, which is a LOT more difficult. Even a good hobbyist translator may not have the skills to translate entire stories of text in a way that's pleasant to read.
I assume the LNs are probably better than the manga in Japanese, but since I can't read it... I'll stick to manga.