Funny enough, they are called "MSF" here in NC too... lol. But seriously, you may not need to take it, but it will only help you out. There are some differences between dirt bikes and street bikes, the main difference is the riding environment since street bikes, you'd have to pay more attention to your surroundings such as traffic, road conditions, and other hazards. I've learned quite a bit through their in-class portion of the course that I would have never thought about for safety. It is very informative and very well organized safety course.
The MSF course is not operated by the DMV so they know what the hell they are doing. My instructor said that the NC DMV written test was so idiotic that if you followed their rulebook, you'd surely get yourself killed because it had so much missing information and wrong advice on how to ride. MSF stands for Motorcycle Safety Foundation. In most states, when you take it and complete it, you get a certificate to bring to your DMV to recieve a full endorsement as well as most insurance companies, depending on the state you live in, will give you a % discount off your insurance rates.