"tube watts" versus "solid state watts"

>>Tubes are men. Transistors are women.<<

Everybody chant with me:

ohhmmmmmmmmmm............

So if its not clear- the difference in tube and transistor watts has to do with distortion- generally speaking tubes have more distortion, but most of that is lower order which the human ear/brain system does not care about. Transistors tend to have more higher ordered odd harmonics, and while in only trace amounts (100ths of a percent) these are the harmonics that the ear/brain system used to detect loudness, so the human ear is very sensitive to them.

The result is that a tube amp may have a higher percentage of usable power, even though it has less overall power.

In the case of clipping, a tube amp will seem to compress dynamics slightly before audible clipping occurs. With transistors the clipping characteristic is very audible and instantaneous. This is why guitar players, who overdrive their amps on a routine basis, prefer tube amps. In fact, it is the guitar amplifier business that drives tube availability, not high end audio!

2 amps with identical RMS ratings will probably have similar drive characteristics into a resistor.
As soon as you start driving complex loads with current ahead or behind voltage, that's where you'll start hearing significant differences.
Amps which can tolerate such complex loads will have more apparent power.
As a test you could find 2 different speakers of similar sensitivity..make them 91 to 93db rating. Also, 1 speaker should be a fairly benign load and the other as wretched as you can find. Huge phase angles and large impedence swings.
Try a couple or more amps. amp#1 should be a very high quality unit. Nearly any of the 'biggies' should work. Find another amp of similar power. This one should be of much lower quality, but similar RMS power rating. They should both play an easy load to similar loudness levels. However, when driving a difficult load, the better amp will play louder, longer without heating, and provide a much superior listening session.

Distortion usually increases with demand. More Watts = less clipping. Having more Watts, lessens the chances for distortion. On a cost per Watt basis, ss usually offers more Watts for yer dollar than tubes. One could argue that avoiding distortion is preferable to accepting more pleasing distortion. While it's an old fashion notion, and certainly not the end all towards choosing an amplifier, perhaps we should re-consider $ss to $tube Watts as part of this discussion.

To me,most tube amps seem to sound like they have more power than a SS with equal power.Also if I remember right,tube amps have even order distortion vs. odd order distortion put out by SS amps.This may already have been mentioned.