i tend to find, particularly with lower powered tube amps, the sound tends to be more full and rich sounding and more lively at any given volume level than is the case with solid state. Solid state tends to sound a bit dead and less engaging which prompts one to turn the volume up more. That one tends to be satisfied at lower volume levels with tubes, I suspect, makes one feel that tubes are delivering more power than they are actually delivering. Also, most people don't come close to actually using up the massive "reserve" of power from their amplifiers. So, something that sounds rich and lively at low power is not disadvantaged as much vis-a-vis much more powerful solid state amps; the advantage of extra power in reserve tends to be more theoretical than practical.
As long as the tube amp is working at or below about 1/3 or 1/4 of its rated output it will sound sweet and uncompressed. While that power level might see, really low, it is probably a limitation that is breached for only short periods for most listeners not requiring head-banging levels.