The question of whether Directive Principles of State Policy (DPSP) are 'more fundamental' than Fundamental Rights (FRs) in achieving socio-economic justice, as envisioned in the Preamble, is a complex one that has been a subject of extensive judicial and political debate in India. While both are crucial, their roles are distinct yet complementary.

Arguments for DPSP being 'more fundamental' for socio-economic justice:

1. Direct Mandate for Socio-Economic Transformation: DPSPs (Part IV) are explicit directives to the state to achieve social and economic democracy. They outline the positive obligations of the state to create a welfare society, ensuring a living wage, equal pay for equal work, public health, social security, and equitable distribution of wealth. These are the very essence of socio-economic justice.
2. Preamble's Vision: The Preamble explicitly states the goals of 'Justice – social, economic and political.' DPSPs are the instruments through which the state is expected to realize these goals. Without their implementation, the promise of socio-economic justice remains unfulfilled.
3. Non-Justiciable Nature (Initially): While FRs are justiciable, DPSPs are not directly enforceable by courts. However, this non-justiciability was intended to give the state flexibility in implementation based on resource availability, not to diminish their importance. Over time, the judiciary has increasingly read DPSPs into FRs, making them indirectly enforceable.
4. Collective Good vs. Individual Rights: DPSPs often prioritize the collective good and societal welfare, which are essential for achieving broad-based socio-economic justice, sometimes requiring limitations on individual rights for the greater good (e.g., land reforms).

Arguments for FRs being equally, if not more, fundamental:

1. Enforceability: FRs (Part III) are legally enforceable, providing individuals with direct recourse to courts if their rights are violated. This makes them immediate and tangible guarantees against state overreach and ensures a basic minimum standard of human dignity and liberty, which is a prerequisite for any form of justice.
2. Foundation of Justice: Rights like equality before law (Art. 14), prohibition of discrimination (Art. 15), and abolition of untouchability (Art. 17) are fundamental to social justice. The right to life and personal liberty (Art. 21) has been expanded to include various socio-economic aspects like the right to live with dignity, right to livelihood, right to education, etc., thereby directly contributing to socio-economic justice.
3. Judicial Interpretation: The Supreme Court, particularly since the Minerva Mills case (1980), has emphasized the 'harmony and balance' between FRs and DPSPs, stating that they are two wheels of the chariot of social revolution. It has held that FRs provide the means to achieve the goals set out in DPSPs, and DPSPs provide the objectives for FRs.

Conclusion: It is more accurate to view Fundamental Rights and Directive Principles as complementary and interdependent, rather than one being 'more fundamental' than the other. FRs provide the essential framework of individual liberties and equality, without which socio-economic justice would be hollow. DPSPs provide the positive agenda for the state to actively work towards creating a just and equitable society. The Preamble's vision of socio-economic justice can only be fully realized when both are given due importance and implemented in a balanced manner. The judiciary's evolving interpretation has increasingly blurred the lines, recognizing that many socio-economic rights, though initially in DPSPs, are essential for the meaningful exercise of fundamental rights.