In The Rivals In believe the main differences I see in the three prologues was the style. One seemed to be a conversation amongst two characters while the other seemed to be addressing the audience. If called upon in class I would ask this question: why would the authors write three separate prologues? A possible answer for this question may be because all three styles are different that the goals the author attempts to accomplish are different. I know that different styles can reach different people in different ways. Paying attention to style can help the reader understand the writers purpose.
Source: The Rivals (Brief Context