Here are two examples that I find useful in terms of what I would hope for in a good rotary for QC, both in terms of features as well as tonal examples:
And especially around 3:30:
Both the Lex and the Pinwheel have different, but wonderful drive circuits with clear overtones and a richness/thickness that’s so great. The Pinwheel especially addresses and maintains the unaffected guitar tone and adds to it, rather than imposing its own personality on the guitar.
The Strymon really nails the ranges for speed and rates of acceleration for the horn and bass speakers separately, and the counter-rotating directions are really evident in the panning and Doppler of the sound. The asymmetry of the mic placements (sounds like back and side, not left and right symmetrically) really adds to the realism here. Also, having control over the perceived mic distance is really valuable, though personally I would always have the control cranked for maximum panoramic width and close detail.