It's really crazy that the NES demake is actually the definitive edition of the game. But it is, the devs have even gone on record saying that this version is preferred to the modern version.
Because it was designed with NES-like limitations to begin with, remarkably little was lost in the transition. They had to redesign the screens to be narrower to fit the NES' aspect ratio, but this isn't even seen as a downside since the old widescreen rooms were seen as too sparse and slowed down the pacing of the game. So the few changes they had to make were seen as an improvement, actually.
I skipped the PC version entirely, so I can't compare them myself, but I had a lot of fun with this game. When played without assist mode, it authentically feels EXACTLY like a late NES game from 1991, its design sensibilities are legitimately that old-school.
Unfortunately that's not ALWAYS a good thing. Like a lot of games of that era, it clumsily mixes instant-death traps with a healh bar system. Just like the Mega Man instakill spikes of old, it's really frustrating to have all trouble you went to to preserve your heatlh bar be nullifed with one bad jump. If you swallow your pride and activate assist mode you can set it to respawn on the same screen when you die, which makes it less frustrating to drown in the water, but also nullifies the challenge of managing your health bar since you can refill it by dying with no penalty.
A more reasonable compromise would have been that if you hit an insant-death trap with more than 1 health, you respawn at the start of the room with 1 less health. That would have made the deathtraps much more reasonable to deal with, without removing the tension from all combat. And it has precedent in retro games since that's how the old Zelda games handled Link falling into a pit, so authenticity is no excuse to not do it that way.
This little game design hiccup is the only reason I didn't give it five stars. Otherwise it's really very good.