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.
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.