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Pentodes are far more efficient than triodes and with the same bottom line can usually produce 5 times more power. That makes pentodes and solid state transistors a partially monetary issue. So, as an example, if you have speakers that are marketed for handling large amounts of power with low distortion, you can bet they require large amounts of power to reach their potential. In such a case, with say a well damped room, and some easy rather laid back soft dome tweeters, a Pentode may sound overall better because of the extra power and dryer signature.
On the other side, if you've gotten more sensitive (sensible) speakers you would know that they are higher in fidelity, more expensive, and harder to find than normal speakers. But in such a case, the higher sensitivity also means higher transient speed, much more resolving power with the potential to unmask layers and layers of additional detail and crucial harmonics that make the difference between real and recorded sound. In a system like this, more pressure is on your source and cables again because of the much higher resolving power of the speakers. You can and will hear everything that's wrong with any one part of your system and or recordings. This is high fidelity. In this world, the difference between negative feedback and no negative feedback amplifiers is as obvious as listening to your stereo with your fingers in yours ears and then taking them out.
Also in this world, because of the resolving power of your speakers and the higher quality supporting gear required, bells and whistles become setbacks from a sonic standpoint, and the shorter your signal path is the less chance of contamination. Suddenly we want simple circuits with part counts in the single digits and this is where tube amps typically (but not always) excel. Within the tube camp, the Triode will almost always sound far superior and far more natural with the correct timbres and harmonics. In the inefficient system it may and probably would sound dull, soft, and be in a state of constant clipping which because triodes clip so gracefully would be interpreted as a lack of clarity until such a point where the poor thing blasts off and sticks in your ceiling with smoke coming out of its ass.
In my opinion, if a man wishes to set up a personal listening room in his home with the serious intent of creating a perfect 3 dimensional soundscape with perfect frequency balance the top of the audiophile food chain is single ended triodes and either expensive high quality full range horn speakers, or electrostatic or planer magnetic panel speakers. And I'll confirm a secret that you've probably heard before... You've never experienced PUNCH or dynamics until you've sat inside this combination. The detail and speed is breathtaking and if you compared it to huge conventional speakers of you choice, boasting multiple woofers, massive solid state amps, and even a subwoofer with it CRANKED you wouldn't be close.