The main difference is that the light emitting region on a LED is about 1mm squared, while on an LD it's on the order of 1um squared - 1 million times smaller. This difference is enhanced even more because LEDs emit a wider cone of light than uncollimated LDs. (Also an LD emits nearly monochromatic light; I have no info on the bandwidth of LEDs).FYI LD and LED are not "exactly" the same. I don't recommend it, but have you ever stared at an open LD? I have. also if they were the same we would be able to focus the LED like an LD right? just food for thought
michael