The main aim of joining NSS is Personality Development through community services. So , definitely after going for it will result in building you a great personality. And you may need not to opt for personality development classes :p.
By joining NSS you will opt for a journey to discover yourself.
You will learn about your strengths and weaknesses.
You will definitely learn amazing skills and qualities like leadership and team work among people with different streams.
You will get exposure for your works and talents. Even for small contributions and achievements.
You will explore different cultures, mentality and actual situations/problems in different parts of the state, in villages, in different parts of country and even different nations through NSS special camps, state camps, National camps and International Exchange programs.
The work you do will provide you with self satisfaction which is worth of spending time in it. Believe me or not it is the one of the best extra - curricular activity to be a part of.
By doing work in it you will be definitely contributing in building nation.