Contrary to claims here, it’s always been the prevailing opinion of the English community to prefer dad-Nier; so if I don’t want to have a big debate it’s mostly because I’ve had it over and over, as the underdog. But the remaster is coming and I predict that sentiment’s going to turn around once more English speakers actually play “Replicant”, so take this as the post I can link back to in hindsight: (NieR spoilers follow)
Nier’s youth is integral to the story. Before the time-skip, Nier is comically naive: he acts and talks like a Weekly Shonen Jump hero, and it’s constantly contrasted with the awful world he lives in. His interaction with every character is framed around this, it’s why Kaine sticks around him, half spitefully wishing to see him proven wrong, but secretly hoping to see him proven right; it’s why Emil falls in love with him, as the first optimist he’s ever known, and so on. It is not an accident that the villain is called 魔王, and that he turns out to be Nier himself, Nier if he were beaten down to accept pragmatism. “Shadowlord” is itself a step too far in localization: it should literally just be “The Dark Lord”, said with all the awkward sincerity of a Disney cartoon. It is intended that this kiddy JRPG way of looking at things be jarring next to the bleak and not very high-fantasy-like setting.
In the adaptation to dad-Nier they stumble between honoring this boyish personality and having part-one dad-Nier already be experienced and worldly. It’s the worst of both worlds, where you go between wondering ‘why is this middle-aged dad so gullible half the time?’ and also miss out entirely on the impact of the part-one climax and the time-skip: in “Replicant”, the pre-teen, plucky naive would-be manga boy hero is traumatized and changes into a teenaged, socially stunted violent borderline psychopath. In “Gestalt”, a gruff adult man changes into a . . . slightly more gruff adult man? And this is more subjective, but IMO Jamieson Price has basically no variation in his performances in parts one and two, while bro-Nier has two separate voice actors.
If you have only played “Gestalt” and wondered what’s up with why other characters go through uneasiness with dad-Nier after the time-skip when he acts largely the same, that’s why: bro-Nier was introduced to them as Toon Link, and when he comes back he’s a murderhobo. This is why you visit each area in part one, and then again in part two; it’s the whole point of the game, the contrast. The events of the endings play differently, also: one has to wonder if an experienced, grown man might not see his way to compromise, but part-two bro-Nier is a hormonal mess who, despite his obvious madness, also still clings weirdly to his boyhood principles— and there’s no doubt how his journey ends if no one stops him, it’s a dread bearing down on you through the whole back half of the game.
So while I agree that it’s cool to see JRPG protagonists who aren’t high schoolers, “NieR” the game is fundamentally a story about a young man’s troubled maturation. It’s Tarou doing a bildungsroman, a form that’s very popular in Japan, but which he had never done before.