The problem with DVD-R is that it must be played back on a DVD player. And the DVD players and "universal" players that I've heard are not exactly audiophile audio equipment. On the other hand, CD-R often sounds better than production CD. In fact, if you take a commercial CD, extract the audio using something like EAC, then burn to high quality CD-R media like Taiyo Yuden using a good CD burner, the CD-R often sounds better than the original through a quality audio system.
I'm curious about the HDTT outfit. They are using typical commercially released audio tapes of the era, not audio master tapes. Audio quality of commercially released tapes varied, just as the quality of CD audio varies today. And the quality of the tape itself was variable. Most of the audio tapes released were not on the highest quality tape to begin with. Then there are issues related to stretching and print through. Sure you can correct for a lot of things, but HDTT is not professing to do any audio correction.
This is quite different than the practice of going back to the original tape master to do a remastering of the audio. HDTT are not even claiming that they remaster the sound. From what they describe, they are just making good burns from the commercially released tape to CD-R and DVD-R media.
Is it better than a remaster that is derived from the original audio master tape? Well, maybe we will find out. The Steinberg Brahms 3 is available in a box set of CDs from MCA Classics that was remastered from analogue. I think the remastering was done quite a long time ago, but the commercial tape used by HDTT is likely just as old. It might be worth a comparison.
Actually, the claim of "HD" by the HDTT outfit is questionable to me. What is it about their process that creates higher definition when working from a commercially released audio source?