Many assume bulb and reflector are the primary factors in maximizing light output. Not discussed thus far is the H4 glass lens that one would assume is designed/maximized for the light produced from an H4 bulb and reflector.
While the LED bulbs might produce more lumens, does this actually translate into a light pattern that is deeper than H4 bulbs? I haven't seen that test thus far, only anecdotal opinions.
Here's my anecdotal story. Some years ago, I replaced my H4 Cibie Z Beam units (NLA?) with Bosch H4 light assemblies due to growing rust in the reflectors. I noticed a difference in light output. The Z Beams were brighter and the cutoff delineation more distinct, even with partially corroded reflectors. What was the difference? Bulb, reflector or lens?
Start here:
https://www.google.com/?gws_rd=ssl#q=cibie+z+beam+headlights
... or here:
https://www.google.com/?gws_rd=ssl#q=cibie+z+beam+vs+bosch+H4+headlights
MHO,
Sherwood