What matters most to you? Being challenged by the competition and thereby motivating yourself to push harder and longer? Or winning concrete awards for your efforts, such as the 1st places prizes, whatever they may be? If you move up, your rewards won't be something you can hold in your hands, but will still be significant to you, in improved skills and challenge. With 5 races left to go, are you going to be bored if you stay in the beginner class? You sound like you want to move up. You sound ready for the challenge. Why not go for it? Then you'll know what to expect and how to train for next year.
Good luck either way!
Annie