Both the fields have potential in their way. Now you have to decide which will be right for you for that you have to know the basic working principle in both the fields.

Let's start with Biotechnology. Biotechnology is a field that prepare products from biological systems. This field has implications in the field of pharmaceuticals also. Now in this situation of pandemic , you have come through biotechnological innovations in producing the vaccine. The fields also have contributions in the interdisciplinary fields like Genetical Engineering , Biomedical engineering etc. So you can understand the field has direct industrial application. So there is chances of getting job after completion of your B.Tech.

Now if we discuss about Microbiology , the field mainly dealt about learning the process of development in the microscopic organisms. The field nurtures knowledge and helps in the process of fermentation , Production of Anti-Biotics , Biopolymers , inventions of prebiotics. So the basis of the subject is to analyze microbial organisms. As you can see this has industrial application but getting a job after BSc Microbiology will have less chances but having a MSc will definitely suffice a great position.

Now regarding your question. You have to decide what is the perspective of your studying. You have to find what interest you the most. Both the courses are great and this course will become excellent once you have the interest in it. So decide which satisfy you perspective of studying and just pursue it.

Hope my answer helps you. Wish you all the best for your future endeavors!