If you have to take the class again, and it will be the same professor next time, I would take the final. That way you can get a rough idea what questions the prof likes to ask and in what manner. It's like taking a practice SAT or LSAT or NAVLE or whatever. Use it as a tool to find where your weaknesses are, that way when you take the class again you know exactly what you need to study up on and when you need to ask questions. Also, if you study hard for the final and shoot for that A, imagine how much easier the class will be next time around because you've already committed that information to your brain.