As it looks, UPSC has worked hard to bring out a balanced syllabus and it is difficult to say that it has some juice for any particular discipline.
Some topics covered in General Studies Papers I, II, III and IV may look to be aligned to optional subjects like Public Administration, Political Science & International Relations, Geography, Sociology, Psychology or may be Philosophy but, my sense says UPSC has taken an approach that include inter-relation among topics and across disciplines.
The emerging environment requires a rational approach towards General Studies preparation and choice of optional subject.
Do not fall in trap with some optional subjects depicting exciting overlap; there is no rush. The Main Examination pattern is new, understand the complete-exam-plan and then only make an informed choice.