For a beginner, it is a difficult decision and we sincerely hope that you have narrowed your choice to Public Administration and Sociology after due considerations.
Both Public Administration and Sociology are very good optional subjects and have delivered excellent results and high scores.
Even in new format, both these render some support in General Studies preparation due to some syllabus overlap.
Public Administration is an evolving subject and highly dynamic in nature. But, looking at the recent Main examination 2012 question papers, Public Administration threw many surprises and the marks scored by most of the aspirants does not give conviction in picking Public Administration as optional subject.
Sociology is a pure social science subject and can be managed with in limited period if you have interest in it. Good writing style would add value to your answers in Sociology.