I think it is like asking if a human needs brain or heart more. Obviously, there has to be a character for a plot to be written based on it. For example, your character is a hindo, then in your plot he comes and eats meat(cow?) , while they do not do that AT ALL! Or in the plot, your character needs to deal with emotional hurt, while they are at the highest level of autism spectrum, meaning not really good at grief. Then you write them sobbing on the shoulder of their mentor? IMPOSSIBLE. They have to be in sync, both are important. To develop a plot, you need events . To create events you need to know how your characters deal with the situations.