All 8 routes ranked from best to worst:

Primrose - She’s the main character I chose when starting up Octopath, and I’m so glad I did. This is probably the most complete story in the game, where every chapter just feels narratively sound. There’s a lot at play here that makes Primrose’s story of avenging her father and fighting the Obsidians satisfying. In Chapter 1, her master, Helgendish, perfectly establishes himself as a total piece of shit, and seeing Primrose put him down so coldly before immediately chasing down the Obsidians was so satisfying to watch. The route keeps up this momentum by showing the influence and power the Obsidians have in the criminal underworld. Plenty of time is dedicated to Primrose’s character and backstory, which gave me good reasons to care about her relationship with her father and thus her reason for vengeance. Even though Simeon’s reveal as the leader of the Obsidians was kinda obvious, I didn’t mind it since the guy’s a delight of a villain once he’s revealed. His demented view of everything in the story as a play makes Chapter 4 of this route my favorite part of the game. He constantly mocks Primrose in the final battle, both in his dialogue and his scripted play being a mocking retelling of her own backstory, which is so powerful that it gets to both her and me. And he does that shit to his dying breath, making it so satisfying when Primrose stabs him with her dagger and the credits roll.
Also, she’s one of the prettiest women I’ve seen in an Asano game, but that goes without saying.

Olberic - Great route, loved every second of it. Olberic is so compelling to watch because you know he had a purpose to being a warrior back then, but now that purpose is gone. I loved watching his journey to find Erhardt because it wasn’t being done for pure revenge, but rather to find his own purpose through understanding Erhardt’s. It also helps that there’s a lot of characters in this route that bounce off Olberic very well, especially in the Chapter 2 tournament arc. I love Erhardt just as much as Olberic because after you meet with him again, it turns out he’s been having the same journey where he became aimless after his revenge until he eventually found a village to protect. The fight against him is one of my favorite boss fights because he has the same moveset as Olberic, making it feel like a proper duel between 2 equals. Chapter 4 is also great too, as it shows him taking his newfound purpose and having that tested against a proper antagonist who stands opposite to his ideals. It even does a good job of noting the Gate of Finis at the end, which is the thing meant to tie all 8 of these routes together. However, it’s also one of the only routes that properly does so.

Cyrus - Yeah, this guy’s awesome. While his route starts off simple compared to Primrose and Olberic, it still stands out in character writing and the story picks up pretty well going into the later chapters. Cyrus just has this infectious enthusiasm for knowledge and being a scholar that I can’t help but root for, and there isn’t a dull moment with his interactions. His journey takes full advantage of his personality and skill as a scholar by juxtaposing him against more selfish scholars investing in forbidden magic and knowledge, and it’s a lot of fun to watch. I especially love the final segment in Chapter 4 where after defeating Lucia, you scrutinize the lost library itself and deciphers a mural predicting the calamity of Galdera. It shows that his route is one of the few that properly ties into the Gate of Finis and Galdera.
Also, I might be the only one saying this, but his voice sounds like a less British version of Liquid Snake.

H’aanit - Her route is one of the simplest in terms of plot, but I loved the execution. Chapter 1 does a great job of establishing H’aanit’s job as a hunter with how she holds the forest in high respect and is extremely dedicated. The other chapters show that despite her skills, she lacks the social understanding that most other people in the world do, which is somewhat similar to Cyrus and just as endearing. At first I wasn’t too fond of the old English dialect she and her people spoke in, but as I saw more endearing interactions between H’aanit and other characters in both her story and the travel banter, she grew on me a lot. I also like Redeye as an antagonist because it gets enough scenes to cement itself as a demon that defies the order of both mankind and beasts, something H’aanit is trying to protect. And when you finally face it, it’s nothing like any other beast or optional boss you’d normally see in Octopath. To reiterate, it's one of the simplest plotlines in Octopath, but very effective for what it is.

Therion - Ok, so I like Therion a lot as a character. His dry and sarcastic nature is just incredibly fun to watch with his interactions in the story and travel banter. His personality combined with his design makes him a character that’s just right up my alley. Which is why it’s frustrating that his storyline is just so basic and played straight. You just go to where the stones are, do a few things here and there to get closer to the dungeon you gotta do, and then some basic plot happens as you either get the stones or don’t. The confrontation against Darius does end it on a high note, his death was pretty chilling. I just wish the game did much more with Therion’s plot. For fucks sake, he’s the thief character of the lot, so of course I’m gonna want his story to have a bunch of twists and turns.

Ophilia - Not gonna lie, this one was a letdown when I thought about it as a whole story. Chapter 1 does a good job of setting her up as a character, and it made me intrigued to see what complications she runs into on her pilgrimage, known among the church as “a perilous journey.” Which is why it’s really disappointing that Chapters 2 and 3 are just filler. Granted, Chapter 3 does end on a cool note by setting up Chapter 4, which I like as an idea, but it’s too late. Mattias’s reveal is pretty weak and he only gets to be a villain for the later half of Chapter 4, so he just ends up being the dollar store version of Simeon. What keeps this route from being any lower is the full circle moment where Ophilia saves Lianna from despair just as the latter did years ago. Her route deserves a point for ending on that touching note.

Tressa - 4 chapters where a cute merchant girl does cute merchant things. Yeah, that’s the best compliment I got for her route, it’s bland. I understand Octopath diversifying it up with the stories, and I don’t mind the idea of one of them being a chill, simple route where you just travel to random places on a journey of self-discovery. The problem is that aside from Tressa being a charming gremlin and her back and forth with Ali, there’s nothing else that stands out about her route. It’s especially egregious in Chapter 4, where the final boss is some femme fatale who shows up with no buildup, steals Tressa’s diary because it’s important or something, and then you fight her while her unnamed master shows up for 5 minutes and gets arrested. What crazy secrets did that diary contain? What were Esmeralda and her master trying to accomplish? Who the fuck even was the master and why was he only in like 2 scenes? Eh don’t worry about it until postgame, the real moral of the story here is that diaries are epic and cool.
Actually, before I get too ahead of myself, the one part about the story I actually really like is Captain Leon. When he talked about his past as a pirate, I was just wishing I could have just played as him instead because he’s way cooler. Fuck cute girl does cute merchant things, I wanna see the ex-pirate trying to do business and sell old shit to other people instead.

Alfyn - This route was so unremarkable that when the credits were showing me the bosses I killed, I forgot about Alfyn’s Chapter 2 boss and thought the game was spoiling me on a Chapter 4 boss I hadn’t fought yet. My main problem with him is the inverse of Tressa’s, where even though his story had potential to be interesting, Alfyn himself is just basic and wooden as a character that it drags down the experience. I saw potential in Chapter 3’s ending, where he starts questioning his own selflessness and goes into a depressive slump. That got me hooked onto the rest of the story, but then I was immediately disappointed when that slump of his just came and went thanks to the power of one letter from his friend that he just now found in his bag at a convenient time, which just feels like a lame and contrived way to make Alfyn not sad anymore. And that was near the end of the chapter, so there’s barely anything else to save it. So in general, I guess you could say he's a selfless pharmacist who does selfless pharmacist things, but that already sounds better than what I got from this storyline. Actually, just like Tressa with Leon, I would rather just play as Ogen, since his backstory and post game side quest was also more interesting than Alfyn’s whole arc.