A firm’s competitive behavior is an important topic for practitioners, theorists, and policy makers. Among the explanations of firms’ behavior is Michael Porter’s model. We have presented this model along with some alternative approaches: Structure-Conduct-Performance, the New Industrial Organization and Game Theory, the Resource-Based Perspective, and Market Process Economics. These approaches are discussed in terms of their relations, similarities, and differences relative to Porter’s model. In our comparative discussion, we support the use of Porter’s model to evaluate firms’ competitive behavior. Our reasons for this support are this model’s popularity, well-defined structure, feasibility, clarity, simplicity, generality, and its complementarity to two other main approaches. We find the Porter model to be a convenient approach to the firm’s competitive advantage and strategy.