Tube Power vs Solid State Power

Tube amps tend to be optimistically rated such that an amp rated at 40 watts will only output that amount with quite a bit of distortion; in that sense tube amp watts are less, not more than solid state watts. But, tube amps distort more gracefully (mostly low order distortion), and they tend to compress (not get proportionately louder) rather then sounding harsh, so one might be tempted to push them closer to their rated power.  To me, great sounding tube amps sound more alive, particularly at lower volume levels, than top solid state amps, so one is satisfied with playing at a lower power level.  Hence, the tube amp tends to sound more powerful than its rating.

I am more in the camp of tube vs. solid state matters the most when it comes to the amp, not so much the sources or linestage.  While I prefer all-tube, I think that finding the right amp is the most important thing when matching electronics to one's chosen speaker.  If the speaker is reasonably efficient, and if one does not have an extremely large room and insist on playing at rock concert levels, I personally like tube amps.  In the somewhat extreme circumstance where more than 100 watts is really needed, I might consider solid state because I don't like high-powered tube amps.  For most applications, I think one can find a good pentode/tetrode pushpull or output transformerless tube amp, and with high efficiency, single-ended triode amps can be added to the list of candidates.

When it comes to the amount of power needed, I think more people err on the side of going for "more" when they should have been emphasizing "better."