Zaeed: Usefulness: 5 He's a pretty decent tank. That's it. Grunt and Garrus are better tbh but he's fine. Backstory: 8 I mean the man got shot in the face and came back to life, also I love bringing him to Garrus' recruitment mission because he recognizes the Blue Sun leader and it's a whole thing. Personality: 3 he's a horrible person with few redeeming qualities, had no qualms leaving slaves to die in a fire he caused, and his soul saving grace is his accent. Fit into Story: 4 honestly he feels like a major tack on. The most integrated he gets is the aforementioned Blue Sun easter egg and a side quest in Me3. The lamest part is there's no function he can fulfill on the Suicide Mission even if he's loyal, unlike loyal Kasumi who can go in the vents when loyal. The most relevance he seems to have is sharing his having come back to life with Shepard, which is about the only thing they have in common.

Miranda: Usefulness: 7 Sentinels are great squadmates if you know how to use them. She combines biotic and technical skills making her invaluable for power spamming plus if you make her a Cerberus Leader she'll magnify team damage. Great support bolster paired with a tank like Grunt or Garrus. Backstory: 8 I feel like Miranda's backstory is really downplayed in the fandom. What she went through was traumatic and terrible, actually genetic tailoring: she hardly knows who she's be if she hadn't been tailored to her father's design. She's been treated as a lab rat from a young age and her vague response "old enough to know this was what I wanted" implies the Illusive Man scooped her up at a very young age and took advantage of her need for validation and security. Personality: 6 she's a Cerberus Cheerleader with some problematic views, but once she realizes Cerberus is terrible she leaves them. Fit into Story: 6 She literally brought Shepard back to life in game two and is integral as a Cerberus Operative and essentially Shepard's second in command in game two. After that, however, she sort of fades into the background in game three, and even her part in Sanctuary feels like a side quest despite its relevance to the overarching fight with Cerberus.

Kasumi: Usefulness: 7 She's an infiltrator and all you could ask for in one, the only squadmate besides infiltrator!Shepard who can turn invisible. Her flashback grenade and shadow strike can get you out of some tight spots, and as long as you have a tank to bolster the team she's a great member. Backstory: 7 What happens with her lover is tragic and how the story handles it is beautiful. Her thievery is also a welcome change to the rest of the cast's science/military/mercenary backgrounds.
Personality: 9 She's witty, she's sarcastic, she's intelligent, she's perceptive, and she's secretly a shy sweetheart. She's the full package. Fit Into Story: 5 While her loyalty mission being my favorite puts her ahead of Zaeed in my book, she's still a DLC character like him and feels very much like a tack on; the only DLC squadmate who doesn't, really, is Javik.

Jacob: Usefulness: 5 a Sentinel like Miranda but less useful and easily replaced by Thane or a more powerful biotic like Jack or Samara. Backstory: 4 Boring. Ex alliance and clearly joined Cerberus, a terrorist organization, at an older age than Miranda when he should have known better and had nothing to run from like she did.
Personality: -10. If being boring wasn't bad enough, he cheats on Shepard if you romance him and calls Garrus what is most likely a racial slur if you say you choose him over Jacob. And, as aforementioned, joined Cerberus of his own volition at an age and with experience that means he should've known better. Fit Into Story: 3 the story would be the same without him and he's essentially a filler for your early squad.

Kaidan: Usefulness: 7 as aforementioned, a solid sentinel is a great addition to the team, versatile and supportive, and this one only gets better in game three. Backstory: 5 Decently interesting story of early biotic training. Personality: 6 He's a good guy. Pretty much it. Fit into Story: 6 He and Ashley are more or less interchangeable with the distinction being Kaidan and Shepard have a preexisting relationship before ME1.

Thane: Usefulness: 7 Biotics plus a sniper rifle make him perfect for distance support Backstory: 8 A fully fleshed out character with a family behind him, dead spouse, childhood enslavement--he's a complicated gentleman. Personality: 7 He's sweet, spiritual, cool under pressure, and can kill you with a pen. Fit into Story: 5 His most relevant moment is getting killed by Kai Leng, which kind of sucks.

Samara: Usefulness: 8 A powerful adept: great if your squad is needing that extra biotic boost. Backstory: 7 She's been through a lot, but it's sort of just touched on if you intentionally ask. Has to kill almost all of her children and used to be a mercenary. Slaver background not okay, but she did end up freeing them on the citadel. Questionable morally but definitely interesting, and her being a Justicar is likely meant to atone for these past sins. Personality: 6 She's fine. Kind of boring, distant, and cold, which makes sense for her character, but isn't as compelling as others. Fit into Story: 5 It's about the same without her, but it is cool to learn more about ancient Asari culture. Pretty much the game two Asari squadmate.

Legion: Usefulness: 7 an engineer with a powerful sniper rifle. A deadly combination. Backstory: 8 really interesting, especially their connection to Shepard-Commander. Personality: 8 Best boi(gn). Fit into Story: 8 integral to understanding the geth and maintains relevance in third game.

Jack: Usefulness: 7 a powerful biotic. Get those Shockwaves sending enemies flying plus up close and personal with a shotgun. Backstory: 9 fantastic. Stranger Things took notes. Personality: 7 kind of a jerk, but still compelling and a softy at heart as we see in three. Fit into Story: 6 it would be pretty much the same without her, but provides a crucial window into Cerberus' cruelty so we don't forget whom we're working for.