I just came upon this thread, very interesting.
6SN7 is my favourite tube for rolling, so many different flavours! I have most of the tubes mentioned in this thread other than the TSRP.
thomask, you do not mention the task this tube preforms in your amp, but I think they may be drivers for the output stage. Obviously, the job they preform in the amp will make a big difference in your preferences.
My amp (a highly modified Rogue Audio Stereo 90) uses 6SN7 tube as the driver stage for the output tubes. The type used makes a big difference in the sound of the amp. Here are my feelings on some of the tubes mentioned in your shootout.
Russian 1578 hole plates— not sure what vintage mine are, I have two sets. These do sound very good, with very extended treble and dynamic punch. The sound is a bit larger than life and can cause some fatigue. Mine are also noisier than some other 6SN7s.
Sylvania VT-231—very sweet sounding with excellent treble extension. Definitely light on the bass, but very transparent.
RCA VT-231—-sound more beautiful than life, warm in the middle with good treble extension and decent bass. I like it, but they definitely sounds more coloured than most of the others IMO.
KenRad VT-231 (black glass)—- the best bass of this tube type, sweet sound but seems a little slower sounding than some of the others, possibly because of the emphasized bass. Clear glass sound almost the same,
Raytheon VT-231— there are actually two types, one with Tshaped plates and one with parallel flat ladder plates. The T plate ones are similar to the RCA and Kenrad, with less bass and treble extension, the ladder plate version is brighter with less bass.
Sylvania 1952 “Badboys”— similar to Sylvania VT-231 with more bass, but less transparent and sweet.
Sylvania brown base 6SN7WGT—-good bass and treble extension and dynamics, not as transparent or sweet as Sylvania VT-231, a little dry sounding in the midrange.
National Union black glass—- sweet and warm sounding but less coloured than RCA VT-231, but less treble extension or bass than that tube.
Hytron/CBS 6SN7GT—clear and detailed, a little light on bass and a little dry in midrange.
Sylvania 6SN7W—- I saved the best for last IMO. I do not have the very costly earliest metal base version, but the thick black plastic base version immediately following that tube. Extremely dynamic (far more so than the Sylvania VT-231, but not quite as sweet as that tube), with excellent bass and treble extension. Very detailed and transparent, but definitely not warm like an RCA or Kenrad. Tells it like it is! In my rig (analog source, tube electronics and electrostatic speakers) it works fantastic, in other systems it might be too much (although I do not find it as relentless as the 1578 hole plate tubes).
Enjoy the Roll!