1. Maximum Power Dissipation (1.6 W vs. 1.3 W): The BCP56-16 offers a higher power margin. This suggests it may feature a lower thermal resistance or improved heatsinking within the same package, enabling operation at higher ambient temperatures or under sustained load conditions. 2. Transition Frequency (100MHz vs. Unspecified): The BCP56-16-AQ specifies an fT of 100MHz, making it suitable for high-frequency switching or amplification circuits. The absence of this specification for the BCP56-16 indicates its high-frequency performance may not be optimized or characterized, posing a potential risk in RF-sensitive applications. 3. Operating Temperature Range (-55°C~150°C vs. Only 150°C Max Specified): The BCP56-16-AQ explicitly supports low-temperature startup down to -55°C, qualifying it for wide-temperature environments such as industrial or automotive cold-crank conditions. The BCP56-16 lacks a specified minimum temperature, implying guaranteed performance only above room temperature, with undefined characteristics at low temperatures. 4. Manufacturer & Pricing (STMicroelectronics vs. Diotec): The ST version carries a significantly higher price, typically reflecting tighter quality control, more comprehensive reliability data, and greater supply chain stability. The Diotec variant is likely a cost-optimized part, suitable for reducing BOM cost in non-critical applications.