so far, H4 housings haven't impressed me.
Nobody
knowledgeable ever said H4 headlamps are the be-all, end-all, best headlamps in the world, though that is a common claim among Euro-fans, including on this site (see
here and
here starting at post #14 for example). There are some good to very good H4 headlamps, but there are also plenty of weak ones.
I've tried Cibie ECE housings (aimed by ECE pattern)
Should have aimed these to VOL specs; the Euro aim setting specs are very low in catering to certain governments' unjustifiable singleminded priority on minimizing glare.
I finally found an old timer owned shop with a mechanical contraption for aiming them, and done so on a DOT approved level surface.
I'm assuming you are talking about the BOBI lamps here, because ECE lamps don't have aiming pads for use with a mechanical aimer.
The Trucklite LED housings (set to VOL)
That's not actually possible. The US-spec Truck-Lite LED lamps do not have a cutoff on the left side of the low beam pattern, so there is no way to aim them to VOL. They can be aimed to VOR using the cutoff at the top of the right side of the low beam pattern. How exactly did you aim them?
When I use the Trucklites on low, it makes me wonder whether all my previous H4 low filaments were working at all.
That's not surprising, since you are comparing relatively expensive 2013 technology (the LEDs) to relatively inexpensive 1973 technology (the H4s). Good LED headlamps have much more flux in the beam and give longer seeing distance because of the higher-intensity hot spot. That said, there are halogen headlamps -- there are even sealed beams! -- that give objective performance very similar to the Truck-Lite LEDs you like.
From your description, the only thing I see you doing wrong is trying to aim the Truck-Lite LEDs to the VOL spec.
the 9007 XtraVisions in my '01 Ram & 9007 Nightguides in the '03 Liberty seem much more usable than the Cibie H4's.
This is an interesting comment, because neither of those headlamps are very good ('01 Ram, I am assuming Sport since you mention 9007; '03 Liberty). Still, in a head-to-head versus a good H4, either of them would have plus points and minus points.