I guess it’s just a personal opinion, but I think that the 4KXX versions have much more than 720p of fine detail.
I don’t think it’s a personal opinion at all. It’s easily observable fact.
right now, D+ is best-of-both-worlds stuff. It uses the big increase in detail (and the reversal of numerous bad coloring/de-noising/crushing picture decisions from the last blu) of the “new” 4K restorations as a base, fixes what mistakes those had, and matches the 4KXX raw scans to that look as closely as possible before unifying everything with a great color-correction and film grain pass.
It’s easily the most watchable, and best-looking “original” versions of the OT currently available. It can be improved upon, certainly (Oohteedee’s improved it about 4 times already) but it’s current level of quality is such that only a completely new from-scratch attempt at the 4KXX scans could possibly beat it in terms of detail and uniformity of quality - and that’s exactly what’s happening with 4K77 right now (and arguably, with 4K80, even though it’s never actually been released). Although who knows: if Harmy can rotoscope, mask, and DNR his way to replacing individual elements on the Reliance remaster with 4KXX elements, the D+ versions might get topped there.
But at this point, I think the only other big leap that’s left to make in terms of fan-restoration is audio-based, not visual. If there are ways to even more-closely replicate how the movies sounded back then, or opportunities to directly capture straight-off-the-print the audio stems themselves, that’s the golden ticket, right there.