I'm not really sure how to adequately judge how a dungeon will go just by looking at the map, so I feel like I've got to go by what's pretty. HeroOfFire's is pretty. HeroOfFire gets my vote. (I still have a few issues with it: it's a very large map that falls back on the same kinds of setpieces throughout, and I'm a little worried that parts of it would blur together in practice? This is annoying, because it's super hard to judge if that's really true or if I'm just making up complaints for the sake of it, just by looking. I do like the little artificial islands to the south for the variation they give, and I wish the mainland had more details in that vein. I like the palette and the little baby pegasus tree saplings.)
I'm not sure I understand shuji's dungeon's gimmick or the other details like the sinister smiling NPCs, but that's fine--I assume in-game they'll make sense, and they'll add some interesting spice to the dungeon. But I am not judging for that today, I am judging for pretty. The two tones are a little jarring together--the dark purple walls and floor make the normal beige sand look BLINDINGLY BRIGHT. If the sand is like those Silicate Sands squares in Yuurand that drain your HP as you walk through them and there's like this flicker effect that we can't see on a still screen, then that would make sense! But otherwise, I think the effect would probably work better with a brighter wall/floor color that doesn't contrast with the sand to quite this degree, or alternatively with darker, slightly grayer sand, and maybe some torches so you can still get bright patches to mix things up. Even though I'm criticizing the color choices a lot, I do like the idea of them. All purple all the time's no fun.
I don't have much to say about Lunaria's, sorry. It seems like a perfectly competent classic NES dungeon. I am not really a connoisseur of those! I should still play 6th.