No question, the OG version reigns supreme. At least as of now. While DX added some cool features and a mediocre dungeon, it also changed the entire meaning of secret ending. Spoiler alert, by the way. In the original, when you beat the game without dying, you would see Marin with wings in the waking world revealing that while the game may have taken place in the Wind Fish's dream, Koholint may not be entirely bound to the realm of the subconscious. This twist ending meant a lot to me when I beat the game without dying for the first time. The entire game is set up to convince you that everything is just a dream and nothing matters but at the end, the bitter-sweetness you just experienced as the island faded is quickly replaced by the elation of knowing that, whether it was a dream or not, at least something of the dream also exists in the waking world.
The DX version, of course replaces this ending with the image of a seagull in the waking world and the simple memory of Marin in Link's mind. Again I really hope that the Switch remake fixes this problem.