Which specialization is better for pursuing a Master's degree in Fiqh: Fiqh and Islamic Political Science, or Fiqh of Inheritance?

It is better to prioritize what the Ummah is most in need of. The jurisprudence of obligatory duties (fiqh al-fara'id) is an important science, but it is not extensive enough to warrant specialization in it for a master's thesis. The Ummah is more in need of studying fiqh generally, and Islamic political theory (al-siyasa al-shar'iyya) specifically. This is one of the most emphasized communal obligations (fard kifaya) in an era where Islamic political theory has been distorted, many have come to believe in the separation of religion from politics, and those who are not qualified have monopolized it. Therefore, it is incumbent upon scholars and their students to focus on studying and applying it, and to strive in refuting the misconceptions spread by the enemies of Islam.