***SET***What Is Your Experience With Different Flavors***

I have heard "real" triodes (300B) and pentodes wired in triode (EL34) both sounding great and both sounding poor.  It is very hard to generalize as many factors come into play such as negative feedback, circuit design, power supply, capacitors etc etc. 

Notwithstanding the above, I have had more success with true single ended triode tube amplifiers paired with a correct speaker sounding the best.

^^ +1

Speaker matching is pretty important, as a general rule of thumb the speaker should have enough efficiency so that the amp never makes more than about 20% of full power. This is so if you want to really hear what the amp is about.

With SETs the smaller the amp, the better. This is because it is very hard to get bandwidth with single-ended output transformers. Initially, the 300b was king; by the late 90s the 2A3 took ascendancy; now days the 45 is highly revered.

+ 2 to me it's less about tube type or topology and more about design, execution, output transformer, and power supply quality. I had well regarded 300B monos I didn't care for, I have an EL34 triode wired Class A pushpull amp that sounds fantastic.