This paper presents a market-based transmission expansion planning model and compares it with a traditional reliability-based transmission planning model. Reliability-based transmission planning tries to install new lines at minimal cost while fulfilling system reliability criteria. Market-based transmission planning, on the other hand, seeks investment opportunities so that network expansions can generate more economic benefits than the costs. Benders decomposition technique is employed in both methods, and their master problems and slave problems are compared, respectively. The two models are applied on a five-bus system and a thirty-bus system. The results show that the market-based transmission planning method is better in terms of relieving system congestions, enhancing market efficiency and reducing load payments. The scalability of the market-based transmission planning algorithm is also discussed in this paper.