NagiHono Round 3 LETS GO!!!!
Toei Magical girls against Toei adapted magical girls, tbh I would not be insulted if they lost here. They are against HaruMichi for crying out loud, they're a decade older and literally canon but I still think NagiHono can give them a run for their money.
First off, Nagisa and Honoka are the main characters, not side characters. They are the most important characters of not only their own show but the whole franchise. Their relationship with each other is constantly developing throughout the first part of the show. They start off really awkward with each other, but throughout circumstances, both Precure and school related are forced to work together, they start to form a bond but hold each other at arms length, but wanting to get to know each other. It's not until episode 8 where they start to call each other by first name after they've already killed their first villain. But their relationship continues to grow as they spend time with each other, get introduced to each others families, support each other in their hobbies, and participate in other school/class events together. By episode 42 there is no longer any shadow of a doubt on how important these two are to each other.
Besides all the precure stuff they're just normal middle school girls with families and friends and school. Who think more about romance (well Nagisa does), than actually partake. Nagisa's captain of the lacrosse team and grows into a strong leader. Honoka's president of the science club and always tries to support her club mates. Nagisa beats up her little brother for barging into her room, her dad tells bad jokes. Honoka has a dog who loves her a lot, and a childhood friend who worries about her. Honoka lives with her grandmother, and cried the first time her parents left her behind, but has grown comfortable with it. They're frequent patrons of a Takoyaki truck. Nagisa procrastinates on her homework, and overspends her allowance. Honoka's bossy and sometimes too blunt. Neither knows what they want to be when they grow up. Everyone finds them to be an odd pair at first, unusual friends for each other, but by the end they've folded their social circles into each other, and respected as an effective duo in school as well. The reason they became Precure is frustratingly vague, and beyond that they have no notable destiny or backstory. Normal girls who just happen to have strong hearts.
But this isn't a poll about whose more canon, its a poll about who's a better battle couple.
I know I've said this a lot, Nagisa and Honoka literally need to hold hands transform, form shields, and use attacks. But I'd like to discuss the other members of their team. Mepple, the chosen hero and Mipple, the princess of hope, are fairies from the garden of hope. They are Nagisa and Honoka's constant companions and besides each other, are the other key to unlocking their pretty cure forms. Those two are deeply in love and will not let you forget it. Despite being deeply in love, Mepple is always at Nagisa's side, and Mipple at Honoka's so their pre-existing close relationship brings gives Nagisa and Honoka extra reasons to spend time with each other, and their relationships are occasionally paralleled or at the very least tied closely together. Pollun is the child they all end up looking after about 30 episodes in, in a lite version of "raising a child together "platonically" ", (with fairy co-parents). And then Hikari comes around. The physical embodiment of the Life of the Queen of the Garden of Light. Fortunately she gets actual adult supervision (who she brainwashes into it but still). She's new to existence and Nagisa and Honoka become her sort of mentors in how to live as well as protectors. My main point is on the magical side of things, Nagisa and Honoka are the main combative power, the other members of their team buff them, but are more the people they protect.
Not to mention the All Star Movies where they are often shown to be a sort of ace team among the cures. And Pretty Cure has SEVERAL battle couples. Nagisa and Honoka are just the original example. Saki and Mai had a fated encounter as children and are also paired with fairies in love. Sora volunteers to be Mashiro's knight, and has to be asked to be her friend instead. Yukari just lets people think Akira is her boyfriend. Mirai and Liko canonically have a daughter together and a full page kiss in the manga. And that's just scratching the surface. Why do these other cures matter? Well they wouldn't exist as they do without NagiHono, They truly are a battle couple among battle couples.
Futari wa Precure is an extremely iconic Magical Girl franchise in it's own right. Everyone knows Sailor Moon, but that's because it successfully made it out of Japan. Precure hasn't had as much success in getting adapted outside of Japan, but that doesn't mean it's not extremely influential there, and its influences have made its way into other anime. Precure gets referenced all the time. Pokemon Sun and Moon referenced it with "Alola DrinKyun". Horikoshi is a precure fan and has drawn a lot of fanart, and referenced it BNHA. Way of the househusband had a Precure parody. There is a Precure inspired Digimon. A vocaloid/precure crossover. Makoto Shinkai is a fan and referenced it in Weathering with You. Recently My Adventures with Superman used Go Princess Precure specifically as a reference for the transformation. Also, Pretty Cure has an official world record. And this is just scratching the surface. If you watch anime there's a good chance you've seen Precure referenced.
Finally: Have some pictures of the girls