The differences between The Sea Inside and The Diving Bell and The Butterfly are that in the movie the man can talk and move his head. The man in the book couldn't even talk. The man in the book suffered a stroke while the man in the movie was at a beach and he jumped into shallow water and broke his neck. The man in the movie killed himself with a drug and the other man died of his condition right before his book came out
The similarities between The Sea Inside and The Diving Bell and The Butterfly are that in the movie and the book the victim is a man and they both are quadriplegics. Both of the men wrote a book about their experiences of being trapped in their own body. Both of the men ended up dying in the end. Both of the men daydreamed all day because they had nowhere they could go.
In my opinion I think that the similarities are more powerful because when people talk about cases in which things like that happen they can prove things if there are more cases then just one better then if there was only one.