No matters at all whatever you choose either BA or BSc. The only eligibility criteria to the UPSC exam is to be a graduate only. What matters the most is your preparation because all subjects and all papers are equally important in UPSC. Whether it is History, geography, Physics, Chemistry, Economics. You have to focus on syllabus and have to stick to that.
You start your preparation for UPSC from initial college days so that you have 3 years in your hand.