The thing that somewhat "saves" low power tube amps, is the fact that due to the lower level of global feedback, they can be run closer to clipping (less crest factor) than solid state amps. In other words, tube amp clipping is much more benign than solid state amp clipping, in most cases.
Feedback is a double-edged sword- it's great at reducing distortion when the amp is below clipping- but once clipping occurs, it actually "doubles down" on the errors- by trying to force the amp to produce more gain (which is what happens when clipping "compresses" the output), it actually causes an even greater degree of distress within the amp (harder clipping) than if the amp had no feedback. This causes all sorts of issues- generation of high-order harmonics (well beyond the usual second, third, and fourth harmonics that usually dominate the distortion of a typical amp- clipping, you can have even significant distortion up into the 10th harmonic or higher), and even stuff like momentary latch-up in some designs of less stability (fortunately, not usually a problem in modern SS amps- but that was a real issue with the first 20 years or so of SS amp designs!)...
So, while you may need to run a 100w solid state amp on an 88dB sensitivity speaker to have enough dynamic headroom (usually, you want 10-20dB of headroom beyond the normal steady-state volume level- and a 20dB increase in level is 100 times the power)- a tube amp may do acceptably well with 30 to 50 watts on the same speaker. Yes, the tube amp clips momentarily, more often than the SS amp, at the same SPL levels- but the consequence of that clipping is much less detrimental with the tube amp...
This is one reason why many of the current modern SOTA tube amps, even higher powered ones, still use more moderate levels of feedback- it's more worth it to do the hard work and make the amp as linear as possible before feedback- which is much more possible with a tube amp than with a SS amp,due to tubes starting out more linear than transistors on an individual component level. For one example- IIRC, the VAC Statement amps only use something along the line of 12dB or so of feedback... they simply don't need a lot of it, to do everything they can do. Hence, a feeling of dynamic "effortlessness", even beyond that of other amps of the same power.,..
Regards,.
Gordon.