Neither really, though.

I don't think Belle develops at all, though she does have a distinct character. Ariel doesn't develop much, but at least she apologizes in the climax for having caused all this trouble. Granted, the apology lasts maybe 5 seconds, but at least she develops slightly. And I mean VERY slightly.

Belle doesn't really change throughout the story, Yeah she sees the Beast in a different light and starts loving him, but she remains the same character. We don't even know what she feels about her vague dream afterwards.

I like Belle way more but I have to admit that her character doesn't really develop. Ariel doesn't develop much either though.

Neither really change, but Belle at least learns to not judge by appearance. Then again, she seemed to know that in the beginning, but she loses her fear of the Beast after learning he does indeed have a soft side. She doesn't run from him anymore, and starts to treat him more like a person than she did before. Overall I prefer Ariel, but neither really are developed.

I don't think either does at all. I always wonder where people see such well-developed characters in them. You don't need a character to be developed to think they're a good one!