As an aside, this isn't really true. LEDs are way more efficient (more watts in visible light and not just heat), but not 100% so. They still get warm and need heat sinks and sometimes airflow, etc. or they can still overheat.

If you leave a LED bulb on for a while next to one that's been off, you can definitely feel the heat difference with your bare hands.

This is especially true at the higher end of lumen output, where you're optimizing for peak brightness instead of max efficiency. The power vs brightness curve isn't linear for a given emitter (and the human perception of brightness isn't linear either).

A LED that's twice as bright will be more than twice as hot. If you have a bright headlight it will typically be in metal housing that also doubles as a heat sink, and probably have internal thermo regulation to turn itself down before overheating.

It's also the big reason why low price LEDs barely last longer than incandescent did. The LED itself is not burning out, but the heat it generated cooks the capacitor used to generate the correct power output, which dies pretty quickly under heat stress.

Nowadays everyone and their mother has a smartphone on them. Place down your smartphone and start recording. Move to the switches and flip them as needed. Check back the recording to provide your answer.

LEDs themselves don't really get warm, but LED bulbs that plug into a wall socket have a transformer in their base to step mains voltage down to something the LED can handle, and that can get quite warm.

Turn on one. Wait a few years. Turn on the other. The one that is off has burned out so it is the first one.

You never touched a LED light bulb uh?