Tony,
You do bring a great point that may be a universal point to be made about URB sound. That yes, there are so many, many factors involved in achieving a good live sound.
Sound of upright unamped.
Type of Pickup
Type of Amp
Type of Cabinet
Room acoustics.
Band configuration (trio, big band, Electric gtr?, etc.)
Style of music
Proficiency of the player
Stage setup (size of the stage, configuration, etc.).
Your point made me realize that I may have poo-poo'd (and scrapped) the Realist too quickly. My variables were: the Realist on a Christopher 403T with Spirocore Weichs with Acme Low B-2 / Clarus, playing fast bop on a tiny stage with a loud, swingin' quartet. I had all the low-end warmth and no little mids and no highs whatsoever. Bottom lilne: couldn't hear myself. I have enough power, I have decent technique. Maybe the Acme was wrong. Maybe a small monitor at ear-level would've helped. Again, lots of variables.
...my 2 cents