Describe ube sound vs solid state

What are the charesterics in comparing each of these?
Thanks Ralph it was something I had believed as it is one of the most noticeable specs you see when looking at a solid state amp spec sheet.
Atmasphere, In that most (all?) speakers draw power with varying impedances and those impedance changes will correspond with sensitivity changes (again we're talking about typical speakers here) unless the amp(s) can change power output appropriately there will be deviations from linear frequency response.

Yes- and enough global negative feedback will allow nearly any amplifier to do that. Its not about being able to double power, its about the amp being able to act as a voltage source. Plenty of tube amps can do that. If we add about 20 db of feedback to our amps they will act like a voltage source too.

Again, the amp does not have to double power as impedance is halved. What it does have to be able to do is cut power in half when impedance is doubled in order to behave as a voltage source.
^It works the same in both directions, and global feedback is not neccesarily a prerequisite.
Tube guy: only tubes sound good

SS guy: jump on the transistors, tubes are the pits.

Where is the truth?

Where it almost always is. Somewhere in the middle.

Myself I choose to shy away from tubes whenever possible. Too many headaches. But I still have some. Go figure. I'd love to ditch them all but at least the ones I have sound good plus of course tube gear is way cooler than not and you can't roll transistors to get the sound you want, but there are many ways to tweak besides twiddling with tubes.
^It works the same in both directions, and global feedback is not neccesarily a prerequisite.

If the output impedance of the amp is low enough then feedback is not required. An example is the Ayre amplifier.

An example of a tube amp that acts as a voltage source is a Mac 30 from 55 years ago.