Are EL34 based amps more musical than KT series based ? Or it's purely a matter of design?

Some people will just listen to 300B based amps and nothing else, I heard.  They consider 300B to provide the purest midrange of them all.

RM-9 wrings quite a bit out of EL-34 but Roger was a genius… Like Gordon Gow and the 6L6 MC240… but really no meaningful conversation is possible without also considering the massively important imo ….output transformers…. 

IF a VPI magic brick on the output xformer significantly alters the sound for the better, you know they skimped….. 

Just a thoughtful guess but given the changes in sound when switching the same kind of output tube by different manufacturers, the make of tube may have as much influence on the sound as the tube type.

Design.