I haven't opted it, still I am going to put my two cents out here for you to consider.

1) You should bear in mind that a lot of people are opting International Relations along with I. Law to cover a part of current affairs and to gain other "reported benefits". That automatically is going to bring the graph of general score down and graph of competition up. Your must be excellent or above that to get a good score. (Consider the example of Indo-Pak history, how it used to be before the reforms--I see I.R becoming the Indo-Pak history post-reform!)

2) My elder brother opted I.R in his first attempt in 2011, he cleared every other subject but failed in I.R. Now, you may think he was probably an incompetent person, but the same guy cleared in 2012 just because he swapped I.R with Socio. and Journalism. Now, this single example may not be enough to prove anything--but what it does prove is that some candidates do fail even after preparing and making their full effort. That just goes to say that this subject can be very unpredictable. This unpredictability can be discerned from its syllabus as well, because it is virtually "limitless". While the syllabus of Pol. Science is limited to a certain well-defined concepts and paradigms.

3) International Relations is more general in nature than Political Science. General subjects always tend to get opted more and your paper has to be exceptional to stand out among all the others.

Take these factors into account before you decide. In fact, if I were you I would opt Computer Science considering the background you have.

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"Everything the light touches, is our kingdom."