Hello there. Hope you are doing good. I would like to tell you that both the above mentioned courses are entirely different field of study. So, your field of interest is of utmost importance while choosing any course.

In general, I can tell you that B.Sc Computer Science will help you in gaining knowledge of various programming languages, database concepts, algorithms, networking etc. If you are really interested in computers and want to make a career out of it by joining an IT company or pursue masters in similar field, then you can go for this course. Talking about B.Sc Mathematical Science, you should have deep interest in mathematics as a subject because a bachelors in specific subject of study will involve intense learning. It has multiple opportunities as a career option such as jobs in insurance, banking, financial institutions where companies requires people with high problem solving and quantitative ability. You can also look for data science, data analytics as a career option where you will be required to make business decisions based on the data provided to you.

At last, you can choose what is best for your by analyzing where your interest lies.

I hope you found this answer helpful. Good luck for your future.