I found this post on another forum (so no source). It does seem to explain why LED headlights don't need to be as bright as Xenon. So my new LED headlights are probably less bright than my old Xenons. However, the light produced allows my eyes to see clearer at night.

It also explains why cars with LED headlights don't need fog lights.
"Xenons are brighter. But please do not necessarily correlate brighter with better performance for night time driving.
It's all about lumens (brightness) and colour temperature (white, blue, purple, orange etc - measured in kelvins).
Xenon run at around 4,000 kelvins which is a yellow / off white colour. LED runs usually at around 6,000 kelvins which is very white and provide a colour which is more representing of daylight (which the human eye is naturally the most comfortable with).
Xenons run brighter at circa 3,300 lumens vs circa 2,500 lumens for LED's. So again, Xenon is brighter.
However, LED provides a better light return (less dazzaling) from objects and therefore are better suited to the human eye (this is very true of road signs). This means clarity of objects in your field of view is better than xenons as the return light is whiter. More lumens do indeed light further down the road but due to the more yellow nature of the Xenon colour temperature, they don't necessarily pick out objects as clearly as LED's. LED's therefore are much better in foggy conditions too (hence why LED equipped cars have no fog lights)."