I get it. I understand (I think) why you feel the way you do and it is a perfectly valid viewpoint. As you pointed out, “beauty lies in the eye of the beholder”. The following comments are not meant as a rebuttal to yours, simply an explanation of why I (!) feel that the SGQ could be considered to be the greatest ever and, for me, they were.
You cite “beauty of expression” as the determinant factor for you. For me there is no less beauty of expression in the playing of the SGQ. However, it is of a different kind; a different aesthetic. It is rhythmically more obtuse. Improvisations are more removed from and less grounded in the melodic and harmonic “centers of gravity” of the composition than those heard in the tunes on KOB, to use your example. Some would say, more adventurous. Don’t get me wrong, I love KOB and it is one of the most important records and one of the greatest bands in Jazz history. During the time of the SGQ Jazz, in general, was in a different place than it was during the KOB era. As always great art reflects the time of its creation and if prefers one particular aesthetic over a more “progressive” aesthetic than that would guide our judgment of one over the other. Those are all things I would say fall under the “in the eye of the beholder” rule. A personal call. I like both aesthetics; probably equally so.
However, for me, it goes beyond that. The level of musical interplay between the members of the SGQ is simply amazing. In my opinion, it is on a different level entirely. There is a level of musical telepathy, musical conversation that happens between the players that is breathtaking. Particularly impressive when one considers how abstract Miles’ approach to a melody could be, as an example. A perfect example of this connection is heard in the very beginning of the live clip that I posted previously. They walk out on stage, no banter, no count off of the tune, no hesitation. Miles simply plays an opening phrase and they take off in perfect synchronicity and it goes from there. Pretty impressive stuff.
One thing that I think is indisputable is the genius of Miles Davis.