The OptoLED can produce arbitrary pulse durations when driven by an external frequency generator..  So can the OptoFlash, but it ALSO has an internal timing circuit that can produce pulses anywhere between 50 microseconds and 100 milliseconds.

What the OptoLED has, and the Optoflash has not, are

1.  Two channels rather than one (of course).

2. The ability to control the average LED intensity by a high frequency pulse width modulation, in addition to setting a continuous current level.  You wouldn't want to control LED intensity that way for channel activation, as it's a good way of getting controlled WEAK illumination.