The only really meaningful 6H30 (also called 6N30) option is the NOS "DR" version of supertubes. The more desireable ones are from the 1980s. They’ve been hard to get, and very expensive, for a very long time. Even 10 - 15 years ago these would fetch $200 per tube. Good luck finding strong, matched sets these days. I’ve been pretty tube crazy this past decade, but even I’ve never tried to fetch a set of these.
That leaves the Sovtek and Electro Harmonic "Gold" 6H30pi as your 2 modern options. I’ve uses sets of both, a few times each. With ARC preamps too. Pretty damn similar in sonics. The EH "might" be a tad warmer. Maybe. Not enough for me to bother much about; I have a couple sets of each in reserve. I do know that cryo treatments, and Upscale Audio’s "Kevin’s Stash" or "ARC Select" premiums never made a whit of difference to me. Upscale’s "Platinum" grade is as good as I’ve ever needed.
I’ve heard of some bold audiophiles using 6N6 as a sub for 6H30 in ARC preamps (e.g. Reference 6), and liking the sound better - BUT reports are they won’t last long, indicating they’re being run harder than they were designed for in these amps. So honestly - that sounds pretty risky to me.