1. Current and Power Handling: The Ic (3A) and Pd (2W) ratings of the 2SC5824T100R are double those of the BCX5510TA (1A, 1W). While the former can handle higher load current and power dissipation, directly substituting it into a circuit originally designed for 1W would not utilize its full capability. More critically, it could pose an overheating risk due to insufficient PCB thermal design for the higher power level. 2. DC Current Gain (hFE): The minimum hFE of the 2SC5824T100R (180) is substantially higher than that of the BCX5510TA (63). At the same collector current, the former requires a smaller base drive current, reducing the burden on the driver circuit. Direct substitution would likely shift the circuit's operating point (e.g., saturation depth, linear region gain), necessitating recalculation of the base bias resistor. 3. Saturation Voltage Test Conditions: Both parts share the same nominal Vce(sat) rating (500mV). However, the test condition for the 2SC5824T100R (2A/200mA) is far more stringent than for the BCX5510TA (500mA/50mA). This indicates the former offers superior conduction characteristics at high currents. In low-current applications (e.g., <500mA), its actual saturation voltage may not provide a significant advantage. 4. Cut-off Current (ICBO): The ICBO of the 2SC5824T100R (1µA) is an order of magnitude higher than that of the BCX5510TA (100nA). Under high-temperature or high-reverse-voltage conditions, the increased leakage current of the 2SC5824T100R could have a minor adverse effect on circuit thermal stability or off-state power dissipation.