A Beginners language course assumes that a student has little to no prior exposure to the different aspects of the language. Because of this, Beginners language courses (including Chinese Beginners) constitute an introduction to the language. This means that different aspects of the target language are introduced to students (a number of whom perhaps for the first time) and the language is explored at a less complex level, which is also reflected in the lower difficulty of the HSC exam. In the case of Chinese Beginners, an example is the maximum word limit for sections that require a response in Chinese, being 150 characters.
On the other hand, a Continuers language course assumes that the student has more significant exposure to the different aspects of the language. Because of this, they are designed to expand the students' existing knowledge of the language, which means that the language is explored at a more complex level. This is also reflected in the higher difficulty of the HSC exam. Using the same example in the case of Chinese Continuers, the maximum word limit for sections that require a response in Chinese increases to 250 characters.
Based on this information, your post as well as the difficulty of the Chinese language, it seems that Chinese Beginners would be the subject that you should take (assuming that you are eligible to take it). This is because your current knowledge of Chinese seems appropriate to study the language at this level, potentially resulting in a more manageable workload and giving you a better chance of performing favourably.
I hope this helps!
