Rapid growth in electricity demand from data centers and transportation electrification has introduced significant uncertainty into long-term resource planning. This technical brief summarizes recent EPRI research comparing deterministic and adaptive planning approaches for managing large, uncertain loads. Deterministic planning optimizes for individual scenarios, while adaptive planning identifies a near-term action plan and a roadmap for future adjustments as conditions evolve. Using stylized load scenarios, the analysis highlights how resource portfolios differ under each paradigm: adaptive plans tend to favor greater resource diversity, earlier investments in solar and short-duration storage, and slower retirements of firm resources. These findings underscore the importance of high-quality scenario development to support robust planning. Adaptive planning offers a promising complement to traditional methods, enabling flexible strategies that hedge against a wide range of futures while balancing reliability, cost, and decarbonization goals.