This study presents a strategic evaluation of two competing investment pathways within the Persian Gulf Petrochemical Industries Holding (PGPIDMC): (A) upstream hydrocarbon field development versus (B) downstream operational optimization and latent capacity activation. Based on real operational data from 9 key units during 2025–2026 (1404–1403), the analysis reveals that downstream units operate at an average utilization rate of only 68%, equivalent to a latent capacity of 3.6 million tons/year of petrochemical products. Simultaneously, a structural feedstock gap exists: upstream supply (4.4 Mt/year from Bidboland and Hoyezah gas plants) falls short of current downstream demand (5.0–5.5 Mt/year), with the gap projected to widen to 2.5 Mt/year if latent capacity is activated. A multi-criteria decision framework (MCDF), aligned with ISO 55000:2024 and IEA 2025 guidelines, demonstrates that Option B (optimization) requires only 20–30% of the CAPEX of a new field development, achieves 85–90% utilization, generates positive cash flow within 18 months, and reduces feedstock consumption per ton of product by 5–8%. The proposed two-stage roadmap prioritizes short-term optimization (1404–1406) to generate cash flow and de-risk the system, while simultaneously launching feasibility studies for targeted upstream development from 1407 onward.