1. Saturation Voltage (Vce(sat)): The PBSS4160T exhibits a lower typical value (250mV vs. 400mV @ 1A). Under identical load current conditions, the PBSS4160T dissipates less power and generates less heat when operating as a switch, contributing to higher system efficiency. This difference is particularly significant in high-current applications such as switching power supplies or motor drives. 2. Maximum Power Dissipation (Ptot): The PBSS4160T is rated for 400mW, compared to 350mW for the CMPT491E. This indicates that under the same ambient temperature and heatsinking conditions, the PBSS4160T can handle higher power dissipation, offering a wider Safe Operating Area (SOA) and greater thermal reliability margin. 3. Transition Frequency (fT): The PBSS4160T has a higher fT of 220MHz versus 150MHz for the CMPT491E. The superior high-frequency characteristics of the PBSS4160T provide better performance in applications involving signal edge speed or gain-bandwidth product, such as RF amplification or high-speed switching. 4. Manufacturer & Process: The devices are from Nexperia and Central Semiconductor, respectively. This can lead to differences in aspects not fully detailed in basic datasheets, such as parameter distribution (e.g., hFE curves), long-term reliability data, and ESD robustness. For high-reliability designs, it is essential to consult each manufacturer's detailed technical documentation.