Gives nose/forehead kisses: Kaneki gives forehead kisses, Banjou gives nose kisses. This is the binary.
Gets jealous the most: That’s hard to say, really. My thought is ‘neither’, but that’s mostly because, what do they have to be jealous of? People who love Banjou are correct and Kaneki can’t fault them for that. People who love Kaneki... mostly want to eat it, so Banjou just fights them instead of getting emotional. If it’s Hide, they bond instead.
Picks the other up from the bar when they’re too drunk to drive: I’m not convinced either of them can drive. I also don’t think ghouls can get drunk, since they can’t eat grapes or rice or any other things alcohol is made from. Unless there’s like bone marrow wine. Kaneki helps Banjou navigate public transit when he’s too tired or out of it from fighting, though..
Takes care of on sick days: I don’t remember if ghouls can get sick like humans can, hm. Assuming some manner of sickness compatible with ghoul anatomy, Banjou takes care of Kaneki in ways that involve putting too-hot compresses on it and burning the coffee. Kaneki still appreciates it, but when Banjou’s sick it has trouble not instinctively making soup. It still forgets that isn’t really an option for ghouls, it’s the default sickness response.
Drags the other person out into the water on beach day: Banjou makes Kaneki take days off, and Kaneki splashes Banjou for his troubles. Equality.
Gives unprompted massages: I don’t know if either one gives entirely unprompted massages, but a prompt could be something like Kaneki shifting weirdly and making a noise and then Banjou volunteers to work out whatever knots have formed in its back. Kaneki would suck at massages if it ever tried, unfortunately.
Drives/rides shotgun: IF either of them can drive, then Banjou drives Kaneki places, but again: I really feel like neither one has the attention span to pass the test.
Brings the other lunch at work: Hi hon, I brought you a leg, have a good day fighting everyone else in the city! xoxo-Banjou
Has the better parental relationship: They don’t talk about this.
Tries to start role-playing in bed: Kaneki for sure, but then Banjou commits to the idea more intensely than it does.
Embarrassingly drunk dancer: See above in re: drunkenness.
Still cries watching Titanic: BANJOU, my gosh. Kaneki tears up, but Banjou goes through two handkerchiefs.
Firmly believes in couples costumes: They don’t... have time for that... Also I think they’d both think it was silly, honestly.
Breaks the expensive gift rule during Christmas: What’s a money. Being a ghoul freedom fighter doesn’t pay any bills.
Makes the other eat breakfast: Everyone is forever having to force Kaneki to eat, but that is a complicated situation.
Remembers anniversaries: If they lived long enough to have anniversaries, which isn’t the case, I still think both of them would forget. Banjou might remember and be extra sweet that day, but he’s just as likely to remember a month later.
Brings up having kids: No, nope.