Most desirable vacuum tubes for SET amps

yep, the best one is the one that sounds the best to you, the best implemented in the amp, the best matched to your speakers, to your room...

asking these questions -- what is the best speaker, what is the best dac, what is the best cable

ugh

Thanks everyone for these wonderful responses. I feel, 300B got a cult status & many folks are waiting for another batch from Western Electric.

on a side note, I didn’t ask opinion for ‘best’. I’m looking for opinion about desirable tubes. The ‘one’ which everyone is after. It could be for academic purpose.  Need not be the best. Again, it doesn’t matter whether it sounds the best in my system. The desirability has nothing to do with it. It’s what the general public ‘wants’ !!

Many swear by NOS 300B Western Electrics. But they have become rare and upwards of $5000+ a pair. My favorite are 45s in general the lower the power the more magic. But at 1 1/2 watts you need super sensitive speakers.

Again no clear cut answer. Most desirable to who? One could certainly say the 300b is the most popular DHT tube. There are numerous current production brands (With various price categories to choose from) 300bs available. A sign of demand if nothing else. There are probably more 300b amplifiers produced than with any other DHT tube. As has been pointed out, the vintage/original Western Electric 300b is highly coveted and extraordinarily expensive. So to a certain niche of W.E. tube seekers  they are very desirable.
Charles

I have a Decware that runs the EL34, a pentode tube, in triode.  The sound is unbelievably sweet and wonderful.  With the amp I have the ability to tube roll and tried some KT-88's.  The KT-88 totally changed the sound and made it sound too bright, too sterile and the musicality went away.  Look forward to trying other tubes to see what, if any, sound better.  I also have a Dynaco ST-70, also running the EL34 in ultra linear.  I love the sound of this amp as well but if I listen to the EL34 in SET triode and then listen to the Dynaco, the Dynaco then sounds very mushy.  Some may disagree but to me it sounds like Polk speakers, which to me are pure nasty.