...when it comes to accurately stretching out a VERY equal temperament, I have seen perhaps four or five tuners in my career that came close to what a VT can produce.
I’m curious about this statement. What measuring ‘device’ or standard are you using to determine that the VT usually does a better job in terms of final musical quality? And in what way can it be shown to be better than alternatives (assuming the aural tuner in question with an alternative approach has a specific goal they are skilled enough to accomplish).
I take the "final musical quality" to be measured by the resonance of the frequencies we leave, as tuners. Admittedly, it is not a finite term because of the subjective nature of our impressions of what we hear. However, "congruence" is something that can be measured when we begin to combine frequencies that are octaves apart. I am using congruence to describe the result of pitches that reinforce rather than cancel, their respective acoustic energy. In simple terms, how even are the triple octaves, and how much damage did the thirds, or minor thirds, or fourths have to suffer to make them so resonant and clear? The "musical quality" of a tuning is, to me, the clarity that comes from consistency,(mainly the thirds) which gives all like intervals the same identity, and congruence, which promotes resonance and resists dissonance. This is particularly true of the octave, where the span of the piano provides an interplay between the high partials of the bass notes with the fundamental of the upper registers. Width matters, and I consider it a higher musical quality when their widths are aligned from top to bottom. An ETD will give me a number for the results my ear reaches, and that number is a valuable piece of information, since machine is a tool that will not only measure these values, but store them for future use and possible refinement.
The ability to know where the fourth partial of a note is, and how it's relationship to the fundamental of a note 2 octaves above is a simple aural measurement. After tempering, (another facet to this discussion), the ability to continue consistently extrapolating the octaves to A1 and C88 without getting too far from the center of the octave "pipeline" is a rare ability. Aurally, we tend to wander from piano to piano, even if we always stay within bounds. We can measure any tuning to determine how alike the intervals are, Also, to see how consistent the fifth is tempered across the board, as well as octaves and others. This ability to see, with time, how our relationships are forming, is also the ability to gain greater control of what we do, stretch wise. That we can re-create the exact same thing on the piano next time lets us critique ourselves in ways we can't do by successive aural efforts, and I think that helps me approach a higher musical quality.
I am on record, literally and figuratively demonstrating alternate approaches to tuning. In that realm, the programmable SAT allows a consistency in what are interpretive areas of tempering. This allows all the critique to focus on the same artifact. However, I have far less tolerance for looseness in equality in an equal temperament, and the exactitude of the equal-ness is one of those things that make some of us dance with angels on pins. In clinical settings, I have seen tuners, a minority so far, that can stop the lights on a ETD that has been programmed for a particular scale. When the piano is flat or sharp by say, 4 cents in places, and you are tuning it for money, a better musical quality will follow the machine, every time. At least, that is what I have observed. this is because I have never seen anyone, myself included, that can accurately make accommodations in the sub-cent range to counteract the off-pitch areas as we go through them, so that discrepancy show up in the final tuning. Again, I see that as a loss of musical quality in the pedestrian world of non-performance work.