LED test light

Why is the LED test light important for pulsed circuits, I've seen this done with a incandescent test light before. Are you relying on the resistor in the LED test light for safety?

Could be - they normally draw significantly less current.

It's the speed at which the LED turns on and off. Its almost instant, so you can see if the circuit is turning on and off more easily. Incandescent bulbs take quite a bit of time for the element to heat up and start emitting light, so you probably wont see it turning on and off, more likely just a dim glow.