El34 = KT88 = KT120

Sure the KT120 is 2x;'s the size of a EL34.
But in my limited expereince ((thus far,,have 1 more experiement just ahead when my new speakers arrive and I build the cabinet, then further testing of the 3 types can begin) 
You get something nice of one tube vs the other 2, and another of he 3 shines better here, the last is slightly superior in this/that aspect.
6 of 1 /half dozen of the other.
I mean it all boils down  gain here, and give up something there.

Power  tube = power tube. 
I would not make such a  big deal over the comparisons. 
Thats said.
I think for me , i prefer the EL34 of all power tubes (as I've been told its the best of the 3) , Why?
Because its the ideal tube in a  PP amp for a  single wide band speaker. 
But i could be wrong, 
Will test out the 3 tubes in a few weeks. 
I actually could not hear much differences on the Seas speakers. All 3 sounded so very close. 
You might say the Kt120's out shoot the tiny EL34 in the  low bass fq's. 
I have Mundorf caps in the amp, these high end caps  adds a  nice punchy bass to any tube in the socket. 
The EL34 has just about same bass as the huge KT120's. 
I just don't see much difference  to debate the issue. 
El34 = KT88 = KT120

I hope you are kidding … if not, go see a specialist.

Miniscle nuances, 
= same 
Miniscle nuances,= same

To you, I guess so ... I have no reason to believe you are anything but  truthful and I am not suggesting you are not. 

Where you go off track is assuming the rest of us have the same inability to hear the differences when the differences are quite blatant to myself and a few others on this forum.  

Honestly, I thought you were joking when I first saw your comments. 

My amp allows for all three and here is my take.

EL-34 > KT-88 > KT-120

At least that's the way these old ears hear it in my system with my amp.