Optional subject in the UPSC mains exam is of pivotal importance, and being the most crucial part and a determinant factor in one’s selection, one needs to choose an optional subject very carefully. Though it barely matters what subject one should take, which subject is more scoring, or which subject is opted for more in the UPSC mains exam. What matters more is your level of comfortability and interest in that very particular subject and your hold on that. Some subjects are perceived as low scoring; this is all because of one's inability to get a hold on that subject, due to poor choice and inability to give requisite efforts. Certain subjects are opted for more by the UPSC aspirants and are easy to understand and really scoring as compared to other subjects. Below is the list of some optional subjects that will help you to top the UPSC exam.
Public Administration
Public Administration is considered one of the most popular optional subjects among the IAS civil services aspirants, the reason being its definite syllabus that can be covered in a few months. Public administration optional subject also overlaps with General Studies Prelims and papers II and IV of General Studies mains. One must have solid conceptual clarity to understand the subject very well and to deliver the best possible answer in the mains exam.
Sociology
Sociology is a very interesting subject that is easy to comprehend and master provided one works very hard. The syllabus of sociology optional subjects is fairly limited. Being a popular subject among the aspirants there is also a lot of study material available in the market. The subject also overlaps with the General Studies papers I and II, reducing the efforts and quality time in preparing the overlapping syllabus.
Geography
Geography being scientific is a popular subject among science, engineering, and other background students. There is a lot of study material available in the market both offline and online, therefore, best suited for those who are preparing in their homes. Moreover, it overlaps with the preliminary and mains general studies paper I. It is much scoring owing to the technical nature of the subject. One needs conceptual clarity to have a better command of the subject.
Political Science & International Relations
As far as choosing the right optional subject is concerned PSIR being interdisciplinary is one of the best choices for UPSC aspirants, anyone with the right aptitude can take this subject without any specialization or educational background. Being easy to understand and non-technical one can easily get a hold of the subject. One of the most striking features of the PSIR optional subject is that it overlaps with all four general studies papers. So definitely there is an advantage over choosing other optional subjects.
Anthropology
Being scoring in nature, easy to understand, and very interesting in learning, anthropology is the best choice for UPSC aspirants. It has a tangible syllabus and one can finish the whole syllabus within a couple of months and can be revised therefore many times before the exam. There is no dearth of coaching material available in the market. Being static in nature anthropology is easy to mug up and science graduates find it more comfortable and easy to grasp.
Philosophy
Having the shortest syllabus among all other optional subjects philosophy has gained large popularity among UPSC aspirants. One with good effort can prepare for the philosophy optional subject in just a couple of months. It is bliss and a treasure trove for those aspirants whose aptitude is inclined towards philosophy and related issues. Philosophy will prove helpful in essays and ethics papers also; being scoring in nature, one with a good command over the subject will have a definite edge.
Bottom Line
Above mentioned optional subjects are the top-scoring subjects opted for by the majority of the UPSC aspirants. One must understand that what matters more is dedication and diligence toward achieving excellence. Every subject has its good scope provided midnight oil is burned and every bit of the syllabus is rather swallowed and digested to the extent of mastering it. Wish you the best of luck.