Hey,

There is no as such best optional subject for UPSC CSE. Even if we look at the success rate of candidates based on their optional subjects, then, there is not much difference. Optional subjects forms a core of the UPSC exam and can take your name into the final list or can ruin your result. So, apart from searching for best optional, choose the subject in which you have more strength of concepts and knowledge. The optional subject is prove to be best only when you can score excellent marks in it. So, discover the topics of the syllabus and weigh where you can do more good better than the other optional subject for which you are thinking.