Compared to AC transmission systems, DC transmission systems have become an attractive research topic and practical solution due to their higher efficiency, translating into significant energy savings and reduced operational costs over long distances. This advantage, however, brings challenges, particularly in protection systems where high-speed and precise protection is critical, emphasizing the importance of circuit breakers. Circuit breakers ensure the safety and reliability of power systems by quickly isolating faults and preventing damage. In the context of DC transmission, solid-state circuit breakers, known for their fast response times and reliability, are promising. This paper compares the performance of two solid-state devices—silicon (Si) and gallium nitride (GaN)—under the same bus voltage in different circuits. Each material’s unique characteristics impact its DC application performance. Silicon (Si) devices are widely used due to mature technology and low cost. However, silicon carbide (SiC) devices offer lower conduction losses and higher efficiency at higher voltages, while GaN devices are known for high electron mobility and efficiency, though they are more expensive and less mature technologically. By discussing criteria for DC solid-state circuit breakers (such as switching speed, thermal management, and reliability), this paper deduces the pros and cons of each device and analyzes their potential in DC systems. Simulation results show that while Si devices are cost-effective, SiC and GaN devices provide superior efficiency and speed, albeit at higher costs.