GRJ is correct that the outside temperature of the bridge package should be roughly the same for 8A, 10A and 12A bridges with the similar package since they will dissipate the same amount of power. There is a temperature gradient inside the package from the edges to the devices. The bridge devices are hotter than the outside of the package. Assuming that the 10A and 12A bridges are manufactured with larger devices than the 8A bridges the power density in these devices will be less. The lower power density generally results in a lower device temperature resulting in less leakage. The temperature of the devices is very dependent on their physical layout. The effect might be small but there should be a slight advantage using the larger ampere bridges.
Carl
