I agree with everything your wrote through paragraphs 1 to 3, but I don't see how any 9004 bulb inserted into the USA headlights could improve your lighting. With all due respect, I suspect that your praise is due to hope, rather than reality.
Yes, I haven't tried those bulbs, and I can't ever because I've got Euroheadlights in both of my cars, actual Volvo/Cibie's in mine, and the DJAuto's in my wife's (both '93s).
[full disclosure: I've used Cibie H4's of various model iterations for ~40 years, i.e., in all my car's (almost all Volvos) since the early 1970's, when for most of this time they sold substitutes for USA sealed beams -- my greatest disappoint in Volvos was when they adopted proprietary (non-sealed beam) headlights for which I couldn't buy Cibie e-codes for a small fraction of what I paid for these Euroheadlights -- but I spent the big bucks anyway because I just couldn't stand the USA "plastiques" :-).]
But my skepticism about those Philips bulbs stems from my knowing some things about headlight optics. For one thing, the USA plastic headlights have two major flaws, both dictated by USA Gov't ignorance. One of the flaws is that the optics, specifically the placement of the bulb's filament, and primarily the parabolic reflector behind it, ensures that the vast majority of the light output will be directed uselessly at the pavement about a car length in front -- stemming from the fear of dazzling oncoming drivers. This is exacerbated by the second flaw, the lack of a cutoff shield for the low beam. With these headlights, if you reaim them (I tried this first, before trashing them when I bought my Euroheadlights) so that the low beam is directed a little farther ahead (in a vain attempt to make it more useful), the high beam winds up illuminating only the tops the trees -- i.e., the angle between the low and high beam is just too great for both to be useful.
[btw, an excellent review of headlight high and low beams, the significant and contributions of the filament placement and parabolic reflector, and even the minor additional help from the front lens, are all provided in Bosch's "Automotive Handbook". I recommend it.]
Therefore, I am very dubious about how any 9004 bulb inserted in these terrible headlight housings could really provide any real benefit. All you are doing is dumping a greater number of photons "down the drain" so to speak. It still can't provide the optimum beam illumination pattern for low beams and combine it with a useful high beam. And simply having more photons spilling beyond the main focus (and perhaps brightening the periphery of the illuminated field), the bulb is just making glare worse for other drivers.
Unless or until you've tried an e-code or Euroheadlight and realized how their low-beam's very sharp, sloping cutoff illuminates the road ahead (avoiding glare to drivers in front of you yet illuminating, off to the right, road signs, deer and even moose -- not to mention pedestrians and bicyclists along the side of the road), you really can't appreciate what you're missing.
But if you can't install Euroheadlights, you might be much better off (than relying on hopped up 9004's) by bolting a pair of quality fog lights (including having a good cutoff shield) under your bumper (provided that, hopefully, you aim them properly, e.g., the way Dan Stern instructs at his website).
[disclaimer: I've always been a fan of Dan -- he really is a great guy -- and over many years bought many of my aforementioned Cibie e-codes as well as their H4's from him; along with other stuff.]
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