I agree with SweetsTomato.
Fanfics have a huge starting bonus. Even if you never introduce a single source character, you start out with a potentially large fan base. Little to no effort is required for world building. The readers already know the world, the rules, the cultivation system, etc. You start with a large framework that guides your work. On the flip-side, you have limited long-term appeal if the fandom dies off. You're also restricted to that same framework that guides you.
Original novels start with nothing. Everything must be introduced in steps at a level of detail that explains the world, but doesn't bore the reader. You start with many less fans, but may have better long-term growth potential. You have more freedom in your writing, but also must worry about conforming to the rules you create down the line. Poor planning can cause problems, because the author might not know all the rules at the beginning. They create as them as they go. Then the author can shoot themself in the foot later on.
Each group has strong pros/cons. Neither is necessarily better than the other. However, I think it's obvious they should be separately listed and ranked. Is there even much overlap between the two groups of readers? I've only read original, so I'll admit I'm biased. Anyone should take my view with a grain of salt. However, I imagine most fanfic readers stick to fanfic and most original readers stick to original.
Are there any readers of both fanfic and original novels here, while not being an author? They would be able to present the most unbiased opinion.