A Stroboscope works by simply flashing a light at a spinning object and adjusting the flash rate until it looks like the object has stopped. This gives you a speed in RPM that the object is spinning at. It requires no contact to the spinning object so it offers a level of safety for testing spinning objects, like a motor shaft driving a machine or a fan. It is easy and safe to tell precisely how fast they are going, because the flash rate is calibrated to read RPM.
This is a great question for these devices because actually you would think the LED is faster but the Xenon bulb flashes faster than the LED does. Consequently the LED doesn’t produce as sharp of an image when at synchronous flash rates. The Xenon bulb wins this battle. However the LED is likely to have a longer life span, ok?