Firms face a fundamental challenge when allocating scarce human capital between proprietary technological efficiency and social innovation. Social initiatives such as ethical sourcing and circular supply chains help build brand identity and differentiate products, but the transparency they require inevitably leaks operational know-how to competitors. We formalise the strategic relationship between these two investments and show that it is not static: at low commitment levels, the spillover dominates and the two paths act as strategic substitutes, while past a critical threshold, the resulting differentiation softens competition and amplifies the returns to technological investments, turning them into strategic complements. The transition is robust to Bertrand pricing, oligopolistic competition, and fully symmetric games. From a welfare standpoint, the market undersupplies social innovation throughout, and two talent-targeted Pigouvian subsidies exactly close the gap, offering a tractable benchmark for policy design in industries where sustainability and efficiency increasingly converge.