A lot of Brint's content is us watching him have sex with others, to the point where I am not even sure when was the last time he got any action involving the the champ, solo. The game treats him as a bull to the player, a loving partner, and this nonchalant guy, which just leads to an experience and character that feels so uneven as he has to juggle all three, till it seemingly gave up and all we seem to be getting is him interacting with others, while the champ is, at most, a side piece. It is a a fine thing if you like being a cu""k, but it doesn't really help me feel like Brint and I have any sort of deeper bond, which would be fine if the game wasn't so insistent that the PC is heads over heels for him after screwing him once. That only makes it jarring how he has more scenes with some other NPCs than we have scenes of topping him or power bottoming. Also, personally, I'm not a fan of knowing that my "BF" has kids with others.
Cait also has a lot of orgy content and scenes not involving the champ, but hers feel a lot more considerate of still preserving the champ's involvement while also having orgies and threesomes where we take a center stage. Admittedly, a lot of those champ-centered scenes are locked behind having a prick, but her Hana content is sweet and the fact that we have control of if we want to pursue her as a romantic partner or just keep her as a buddy with benefits puts her potential marriage/relationship progression leagues above Brint's current offerings.
Also, on a more personal note: I dislike the double standard when it comes to how the game treats Brint's promiscuous proclivities compared to Cait's. I am pretty sure he sleeps around as much as her, yet she is the only one that gets called a slut. A double standard, if you ask me. Then again, Arona also sleeps around, but she also isn't called that. I guess you are only considered one when you bottom for someone.
Also, to me, the existence of Brienne makes Brint less appealing and vice-versa. He just looks like a worse spouse in comparison since, technically, they are the same character and mutually exclusive to one another. Same thing if Cait had a male counterpart that is a lot more of a traditional husbando. It makes the option you are attracted to seem like a lesser one overall.
I hope this answers your question.