I'm not sure I can give you a decent answer; in low power amps, I'm okay with carbon comps everywhere but I also don't play out, I don't play especially well, and my agent says he's pretty sure I'm not going to play Shea Stadium. I'm saying that the only place I star is in my own backroom. (member bluesypicky guest starring there):
The problem has two parts; what is the standard of excellence and, to a lesser extent, who can know the mind of Leo?
What is good? Most of the '50s/'60s classic amps ... Fenders, Supros, on and on were loaded with noisy, stuffy old WW2 surplus Allen Bradley carbon composition resistors ... 10%ers at that. By comparison, early Marshalls are loaded with metal film resistors. This is a link to a thread on the Gear Page; a long-running thread celebrating amp interiors; everything from Fenders to boutiques to DIYs. If you page through it, you'll see that even today's better-made amps are all over the place on the question of what resistors to use where:
Gear Page link. Your ValveTrain uses carbon film; not good ... not bad ... just making a note.
What would Leo do? Does anybody really think Leo brought all the mfrs in and conducted A/B/C tests of whose parts did the best? Carbon composition resistors have a reputation for noise and grit although some of their trash is subsonic and can only be seen on an oscilloscope. Anality being what it is; there are people who, if they were told there was grunge in the signal and even though they couldn't hear it, would reject the amp.
If you want or prefer the way-back sound, then carbon composition resistors are what you want. If it has to be clean, then the carbon and metal films are the way to go; they are made to tighter standards, are inexpensive and reliable, and do not contribute grit and grunge ... although I like grit and grunge ..