Since I was name-checked, I'll throw-out some things to consider for this new release of Nadia, coming from GKids.
Sentai's now out-of-print version isn't perfect, but it was made from a traditional 1080p master, initially created for the Japanese Blu-ray. GKids' forthcoming, standard 1080p Blu-ray is being produced from a new 4K scan, presumably ordered by series' owner, the NHK (this isn't proven, but Gkids' wording doesn't make it seem like they are behind the scan).
As a whole, Japanese consumers have more readily accepted somewhat aggressive approaches of applying DNR to older shows, which is partially why we've seen so many 1080p releases unnecessarily scrubbed of grain and turned into blurry messes. Also, video producers are beginning to find--in the process of creating 4K video from 16mm and 35mm film--HDR can overly intensify film grain, taking it from a texture-providing element to a major distraction. Unless video-production companies provide the proper hands-on care, we'll likely see more Japanese-produced 4K versions of older anime with heavy DNR.
For this new Nadia, while it is out in the wild, the disc technically doesn't release until 8/2/22, and (far as I'm aware) we haven't received any hands-on reports of video quality.
That said, we do have some comparisons, based on various screenshots. Some examples:
- Individual Screenshots:
Sentai vs.
Gkids
-
Single, overlay image
There's also the official trailer, which is kinda horrendous (
link). Based solely on what is available, for all the video gains in vibrancy, it does look to lose a ton of fine detail. Unfortunately, we can probably expect this new 4K master of Nadia to be the default source for any future discs, even more so if it was created in Japan; and Gkids' version will be the only official release on the North American market in the foreseeable future. I'd wait for some reviews, before writing-off the Gkids' Blu-ray, but for anyone wanting a more conventional 1080p release, you'd do best to find Sentai's edition on the secondary market or import the current JP set (no English subs or dub, however).
Unrelated, regarding Sentai's release of Vampire Hunter D, the company's comment on omitting the streamline dub was, essentially, the Japanese stakeholders wanted a new dub and that there were "challenges associated" with streamline's. You can view the whole statement,
here, if you want to deal with getting past the weird pop-up.