My reasons are primarily thus:
- Though the acts do not necessarily increase in intensity, character arcs become more prevalent.
- Inserting the lighter Olympia act in the middle gives something of a breather for both the audience and the cast. (Except for the soprano playing Olympia, but if she's not playing all three roles (as is the case in most productions) what does it matter where her act falls. If she is playing all three roles, Olympia first might make more sense, but I'll leave that distinction to the sopranos.)
- Nicklausse directly references Olympia in the Antonia act, which makes most sense if Antonia follows Olympia directly. By this constraint, however pedantic, the only two acceptable orders are OAG and GOA. OAG is already one of the two defaults, so I really have nothing more to say on this point.
In a large part, The Tales Of Hoffmann is about the Muse and Stella fighting over Hoffmann's attentions, the muse taking the form of Nicklausse, and Stella taking the form of the three sopranos over the course of the opera. Presenting Giulietta first opens the tales with the barcarolle, possibly the opera's most famous tune, which has absolutely nothing to do with the rest of the story. It's a duet for soprano and mezzo, and presents Giulietta and Nicklausse, not directly rivals in this story, but rivals in the arc of the opera as a whole, in equal prominence, and sets up what I think the character arcs are, carried by the GOA order. Nicklausse, to start, is Hoffmann's loyal friend and sidekick. Nicklausse has Hoffmann's back, and helps him out of a pinch in the end. By the Olympia act, Nicklausse is a bit more cautionary, and attempts to warn Hoffmann about what's going on. Nothing much comes of this, but Olympia is kind of dramatically stagnant across the board. In the GOA order, it acts as a bridge. Were it just Giulietta and Antonia, there would be no progression, the characters would simply stop and jump to the next page. Olympia paces it, and even if the characters do nothing much, allows the audience to take in what's going on. This is good, because by the Antonia act, Nicklausse is much more forward, directly presenting to Hoffmann the choice between love and art, and singing the beautiful Violin aria. Hoffmann for the third time ignores Nicklausse's advice to turn back, this time with truly tragic consequences.
The first two sopranos in this order, Giulietta and Olympia, aren't tremendously tragic. Giulietta's a villain even, conspiring with the villain Dapertutto to steal people's shadows and reflections. Why? I don't know. Dapertutto pays Giulietta with jewels, so I guess she's vain or greedy or something and that's bad. The thing is, it presents the soprano and the bass together. (And at this point, I'd like to raise that Councilor Lindorf really isn't a villain. The one villainous thing we see him do is intercept a letter from Stella to Hoffmann, and while this isn't exactly nice, tenors in other operas have done worse.) Presenting Dapertutto and Giulietta together somehow, I think, makes Dapertutto less villainous. In the Olympia and Antonia acts, the villain is actively working against the soprano. For Antonia, he doesn't even have a motive, he just seems to be killing her for fun. At least with Olympia he was taking his revenge on Spalanzani for cheating him out of money. And with Giulietta, Dapertutto is not targeting the soprano, and even though we are not given a motive for why he wants Hoffmann's reflection, we see that he does not target Hoffmann specifically, but simply as one of his many victims. Dapertutto is more of a presence of evil than an active villain in this regard, and Giulietta's working for him. In this act, Hoffmann is simply an idiot, he should have listened to Nicklausse (this is a recurring theme in the opera), and everyone, if not happy, at least survives.
Olympia has no real tragedy. Coppelius smashes her to bits, sure, but he was doing so because Spalanzani cheated him, and Olympia wasn't even alive anyway. I don't really feel that sorry for the automaton. Now Coppelius does play a mean trick on Hoffmann, and makes a fool of him (though, again, Hoffmann is an idiot in this act, and should have listened to Nicklausse), but Coppelius doesn't really do anything truly evil. Maybe he just wanted to test out his cool augmented reality glasses, and since Hoffmann happened to be hanging around, used him as a test subject. And imagine how good that stunt must be for advertising!
See the world as it ought to be!
Hoffmann tested, Nicklausse approved!
Reduced price for a limited time only!
(I did not think this advertising thing through.)
And this brings us to the last act. Nicklausse makes his/her most desperate plea for Hoffmann to give up. Hoffmann doesn't listen. The character tenor gets an aria. And then we finally get Antonia and Dr. Miracle, and there is absolutely no given reason Dr. Miracle wants to kill Antonia. This is a point I'll get back to later. Here the soprano, the first one to actually return Hoffmann's affections (to recap, Giulietta was trying to steal his reflection, and Olympia was a robot) dies. And, once again, Nicklausse has to rush in at the last minute to save Hoffmann.
This is where the art versus love theme really comes to a head. Because Antonia has an incredibly convenient illness that will cause her to die if she sings. And of course Hoffmann inspires her to sing. (Dr. Miracle gets her to sing by conjuring up images of her dead mother, but that's beside the point.) And Hoffmann is willing to give up art for her. And then she dies, and Nicklausse wins. So in the end, I guess it could be said that we have the villains, especially Dr. Miracle, to thank for Hoffmann choosing art over love, but then the pseudo-tragedy for Olympia and Giulietta mostly results from Hoffmann being an idiot, so maybe not.
And this brings in the major point that in GOA order, as the stories progress, the soprano becomes more tragic, the villain more villainous, and Hoffmann less of an idiot. The stories also become much broader. Giulietta, on the whole, I think is the most complicated plot of the three, with more nuanced characters, and Antonia is the simplest, with characters characterized in simple character archetypes. And right after the tragedy of Antonia, we snap back into the real world, where Hoffmann is telling the story. He's telling the stories in a tavern, presumably having a few drinks, and the explanation for why the stories themselves progress this way is that over the course of the evening, Hoffmann is growing more drunk and distraught, and so the characters become more stylized and the plots less complex, but more emotional. When Hoffmann is finally pushed over the edge telling the story of Antonia, he snaps back to reality. The Giulietta act may appear to work better for bringing him back, as it would have him recognize that Stella is not right for him, and that maybe she and Lindorf make a better pair, but in the state Hoffmann's in at the end of the opera (Nicklausse describes him as ivre-mort, dead-drunk) I wouldn't think he'd be capable of forming a story like Giulietta.
The final remaining conflict I can think of right now is Nicklausse increasing prominence through the three stories, which other than that, become more Hoffmann-centric. If the three stories are supposed to be told as Hoffmann is coming to his epiphany, what's he doing foreshadowing his own tales with speeches from his best friend telling him he's wrong? At this point I'm actually justifying my proposal rather than actually arguing for it, but consider that Nicklausse is the Muse, and, given that he/she's right there when Hoffmann is telling the stories, could easily be inserting (or inspiring Hoffmann to insert) him/herself into the stories. From Giulietta to Olympia to Antonia, Nicklausse does progressively less in the story, and starts talking progressively more about the bigger picture of the opera. Nicklausse is a character independent of Hoffmann's stories, though present in them, and can thus go against the grain of Hoffmann's own storytelling.
So there you have it, The Tales Of Hoffmann in GOA order. To recap, presenting the acts in this order allows the stories to grow simpler and more emotional as Hoffmann drinks in the tavern throughout the evening. The characters become more stylized, and the endings more tragic. Nicklausse becomes more preachy, and in the end, wins for Hoffmann's attentions. On the off chance anyone is reading this, what do you think? Are there any details I overlooked? Let me know!