Describe ube sound vs solid state

Geoffkait, In many ways you are correct. Especially with regard to room anomalies, though with room treatment and room correction, speakers can overcome some of this issue. Most high quality headphones still have cables. Magnets? Some headphones have cross-overs, some speakers don't. Some speakers can be run class A all the way, though I'm not sure just how important that is. Some headphones have multiple drivers, some speakers don't. Some speakers don't have phase issues, (and with regard to this thread, interestingly enough, most of those present a load that tend work better with ss amplification).
Headphones are heard from an unnatural extreme left/right directions, which almost never happens in live music performances. The sound is sent more directly into the inner ear without the outer ear collecting sound in the more natural manner. One of the unnatural outcomes of this is that one often hears the sound as though it's coming from within ones head, missing the natural soundstage qualities of a live performance.
Headphones can offer more precise indication of specific elements of recordings and play back, but ultimately, at least for me, the whole sounds unnatural.

For me, the difference is arrived at by induction rather than deduction. I was never inclined towards tubes or particularly wanted them. But after listening to many different systems over many years I realized the ones that I loved listening to all had tubes--Jadis tubes, Manley tubes, Atmasphere tubes, VAC tubes, and McIntosh tubes. In the mix was Levinson, Goldman, Pass, Classe, and McCormack solid state, which often impressed me with power and authority, but never sent me into a state of "thoughtless joy" with a yearning for it not to end.

If I try to analyze it, the feeling is similar to hearing a chord sequence such as I-IV-V resolve back to the root. There is something so pleasing in that completion that is similar to the feeling from tubes, whereas solid state was more of a matter-of-fact I-IV-V that stopped short of that final completeness. Solid state had more of a Joe Friday "just the facts" while tubes were more of film noir fascination.

So I guess I'm saying that tubes have provided a musical completeness that my brain seems to crave, and this sense of completeness is the difference.

Unsound, the music that your ears "collect" is actually the room- produced information like reflections and so forth, you know, the very things we try to tame or eliminate since they distort the pure sound from the speakers and which headphones don't suffer. Even more polarizing in the Speaker/Headphone debate, as it were, are Tiny Portable systems, even portable FM/AM radios, that have even less problems than ordinary Headphone set ups. I.e., no transformers, no fuses, no house AC, no interconnects and no internal wiring which, as fate would have it, like fuses is connected backwards 50% of the time. The speaker magnets and transformers are BAD in my world because they generate magnetic fields that distort the sound.

The sound we "collect" effect the sound perception in a predictable (and natural) way outside of rooms that is different than the more direct sound that comes from headphones.

Tube amps at the low end of price are more emotionally engaging for opera, tears in the eye at dramatic vocal passages. Solid state requires more money to achieve tear jerker status, more likely to get a mental hand clap than tears.