Net Present Value (NPV) is the most appropriate financial metric for comparing long-term project investments such as build vs. buy options. It helps assess which option provides greater value over time after considering costs and future benefits discounted to present value. PMI recommends NPV as a key tool in investment decision-making during project selection and early planning stages. EMV is best used in risk-based decision-making. EV measures performance during execution. Impact value is not a recognized PMI metric. References: PMBOK Guide - Seventh Edition, Value Delivery System PMI Business Analysis for Practitioners: A Practice Guide ##############################################