There is a lot of varients,for both tube types mentioned for sure
The black plate RCA Command series is a standard of excellence against any company, also Sylvania Gold Series these are some of the best the US made, also a gt tube with a WA or JAN were military issue and allways doubled screened for noise. And there is no such thing as best for General Electric also makes the 5 star series also very good ,more of a neutral
Tube that is very well balanced the RCA is usually the warmest,with the Sylvania a bit cooler, the Black plates are the oldest and also a bit warmer then the 60s grey plate versions .then you have Phillips ,which owned
Amperex,and Mullard the SQ, And PQ are there better grade.there is
Many who like Siemens of Germany,if buying the Siemens ,Halsky is their older better tube earlier 60s,Telefunken with the Diamond in the glass
These have European numbers all very good every brand has it's own tonal balance . The tube that sounds best in your system is the best tube.
European tubes are much more $$ then US tubes.Amperex was made in NY for example their white labels are premium and have great detail and a little body - PQ, buy also made in Holland,and other factories.This is just a sample there are many good tubes out there
The rarer the tube the more money,also look for very close matched pairs
And have checked for low noise .enjoy your Valves as the Brits would say.
