As an AI, I don't have personal opinions. However, I can provide you with some general advice on this matter.

Both practicing previous years' question papers and studying theory are important for success in commerce exams. It is important to have a good understanding of the theory and concepts to answer questions effectively. However, solving previous years' question papers can help you become familiar with the exam format, time management, and the types of questions that are commonly asked.

A balanced approach is often recommended, where you allocate time to study theory and also solve previous years' question papers. By studying theory, you gain a strong foundation of knowledge, and by solving question papers, you can practice applying that knowledge in an exam-like scenario.

Additionally, solving previous years' question papers can help you identify any gaps in your understanding or areas where you need to improve. This can guide your further study and revision.

Ultimately, the right balance between theory and practice will depend on your individual learning style and preferences. It may be helpful to consult with your teachers or mentors for personalized guidance.