Ralph, can a ss amp have such low distortion as to make that comparison not tenable? I suppose a better question would be, have you ever listened to a ss amp without the typical characteristics you ascribe to them?
I have heard one solid state amp that was quite musical- it also cost $100K and made 100 watts total. It was also zero feedback. It was better than most tube amps I have heard.
But it is the exception by far. I've yet to see a solid state amp with such low distortion as to not be bright- in fact it seems that the lower distortion units are more irritating to the human ear. That this occurs is nothing new- audiophiles have been commenting on this for decades.
Norman Crowhurst wrote about this issue many years ago- back in the 1950s- we are not going over new ground here...
I am not an advocate of 'distortion of tubes' either; I prefer as little distortion as possible, but I am pragmatic in the understanding that distortion is part of the tonality of any amplifier because that is how the human ear behaves and all amplifiers have distortion.