There is no comparison. The SCCA will have a much bigger, safer course, that will allow you to learn more about yourself as a driver and your car. The SCCA events have much higher speeds, and are much more organized. You will have to work, but only the same amount of time you run, and in the end its not hard and well worth it for the fun you have. Dont worry about rules or classes, most regions have novice classes and are more than willing to help you figure out where you stand.
When is the right time to start at an SCCA autocross? If you're asking that question you're ready!