If I got a Hell Razor, I would go 6L6 also. The HR is a modern high gain, preamp-centric, fire breathing metal amp all about huge crushing tones. To me, 6L6's have always been better at pairing up with that kind of sound. The extended highs and lows of 6L6's relative to EL34's, and also a 6L6's tendency to not mush up the mids at high volumes like EL34's can, seems like a better fit for that kind of sound.
Granted I'm talking about like a 2% difference in sound. I have an EVH Stealth 100w (which has 6L6's) and an EVH EL34 100w, and when I A/B them I cannot emphasize enough how small the differences are between those amps.