None of this really applies to solo guitarists. If the guitarist is good enough, the music speaks for itself, if not, then all the showmanship in the world won't compensate.

I would refer to the esteemed Tony McManus. Nobody would ever describe him as a showman, but few people come away from his performances without feeling stunned and exhilarated, simply by the beauty force and energy of the music.

For lesser mortals, however, I would agree that showmanship is a vital component of performance.

Murray