That is the most tricky decision one has to face. In my view, CSS is in real sense is the game of scores and getting allocation in top cadres like PAS,Police etc. Political science has a lot to offer, this advantage comes at the cost. A student with Political Science background can opt Political Science, I. Law, C. Law, I.R, Pub. Admin and even has better understanding of subjects related to law studies and histories. In this scenario, the rational approach to deal with this situation is to deeply go through past papers, reports of PPSC about past years scoring trend and ones aptitude and interest.
In fact, CSS is the game of scores and it dies not require candidate's vastness and depth of knowledge in the subject. Last few years trends demonstrate that Psychology, Geography, I. Law, Regional languages were the most safe choices.
Lastly, one must hear different views, but he should opt the subjects which he thinks are suitable for him. And, please do not try to accommodate variety of views by others. Apnay dil ke suno.