1. On-Resistance (Rds(on)): The FCP400N80Z features a 400 mΩ Rds(on), lower than the 650 mΩ of the FCP650N80Z. At the same current, this results in significantly reduced conduction loss, lower temperature rise, and higher overall efficiency for the FCP400N80Z. 2. Current & Power Handling: The FCP400N80Z offers higher continuous drain current (14A vs. 10A) and maximum power dissipation (195W vs. 162W). This indicates a greater power handling capability, providing higher design margin and improved reliability. 3. Switching Performance: The FCP400N80Z has a gate charge (Qg) of 56 nC, substantially higher than the 35 nC of the FCP650N80Z. With the same gate drive voltage, this may lead to slower switching speed, increased switching loss, and imposes a higher peak current demand on the gate driver. 4. Input Capacitance (Ciss): The Ciss of the FCP400N80Z is 2350 pF, higher than the 1565 pF of the FCP650N80Z. This further confirms the need for a more robust gate drive in high-frequency switching applications. Inadequate drive strength could limit the maximum switching frequency and increase drive-related losses.