First of all, Jerry had NO power tubes in his Twin Reverb! Not since about 1968. Around 1969, preamp out jacks were added going to McIntosh power amps which drove the speakers, and WERE tube MC275's and later MC3500's at first, but around late 72 were switched to solidstate MC2300's, which he never stopped using until his death.
Preamp tubes, I have a friend Simon who is the son of a Prankster and friend of all the GD crew was given one of Jerry's Twins and he said it had 60's-era RCA's, but I don't know if that's what they would have used all the time. I know they purchased huge wholesale quantities of military surplus, so there may have been a lot of sylvania and/or G.E. as well. I'd be interested to know.
Google "Tube Primer" with "12ax7" and find a very informative online document , and and sift through some of those explanations and comparisons... bear in mind the guy works for Groove Tubes but he presents some pretty unbiased stuff imho.
Basically V2 is the tube that affects tone (V1 is only for the normal channel and you can pull it and get a slightly hotter reverb channel) and I really like an RCA in there, but I also like certain G.E.'s , I go back and forth. At one point I was using a Westinghouse of Hungarian manufacture but it actually fried on me, one of the only times I've had a preamp tube fail.
"There, in huge black letters, was 'The Grateful Dead'. It just... cancelled my mind out."-Garcia