The whole Yennefer or Triss thing is very easily decided; Yennefer for Geralt and Triss if you, the player, prefer her. I really like Yennefer as a character and find her personally attractive to me, Geralt too for that matter XD. I do find it surprising on the poll how an equal number of book people chose Triss, each to their own ig? I actually like Yennefer more as a character than Geralt, like way more. I'd happily read a book with her as the main character for a change, just more Yennefer in general is welcome. She has her complexities that make her interesting, and you can understand her actions and decisions due to her life experiences (and I prefer female characters ig) and how she was made into the sorceress we see. She's has her walls almost always so she can guard her feelings and not be hurt (which is why she can come across as 'mean' cos in the game they kinda reset her and Geralts relationship a bit and she doesn't know where she and Geralt are at the moment, and feels hurt with what her supposed best friend did), and like most mages is aloof and quite rude to regular people. Doesn't mean they're all awful, terrible people, and neither is Yen. Hell, she's probably one of the nicer and selfless mages in the entire series with what she does for her family (Gerat and Ciri, even that random, pregnant Skelliger).
I feel somewhat the same about Triss, she too has her complexities and flaws, no one in the witcher series is perfect and have done bad things so it feels so dumb when people lump all that onto Yen and hold it against her. I don't think Triss is a bad person. Perhaps a little influencible/naive (her idealism towards the lodge no matter what that would mean for Ciri, also the people she likes: Yen and Geralt) selfish and a little opportunistic (i.e Geralt but that's mostly the game stuff), witcher 3 is her redemption and she's pretty cool in it and it's her best portrayal, a good friend indeed. I just personally don't think she's as attractive as a love interest (maybe if she had her actual book appearance, I would feel differently), and I think she's a little more bland in terms of personality and character when compared to Yen, who you could say has more 'flavour' I suppose. As I said, I think Witcher 3 is Triss' best portrayal, but it feels kinda like a generic hero save the day thing, y'know? I care more about finding Ciri and reuniting her family.
I can understand game-only players picking Triss, both due to her presence in the first two games and the player's potential history playing them. She comes across as a more typical, perfect, nice, lovey-dovey gf stereotype who isn't as, I suppose, "imposing" as Yennefer? While for book readers or people who know their lore, they obviously know more about Yennefer: her character and relationships, everything. So they're more likely to go for her to bring her back to Geralt, or they already liked her. What surprises me most is how some book readers didn't go for Yen. I can understand if they wanted a change and either had a thing for redheads or liked Triss' portrayal, whatever, do what you want. But those of them who still actively dislike Yennefer, despite reading everything and, in turn, learning about her as a character, her motivations, her actions, why she is the way she is and her shining moments of genuine care. Both she and Geralt grow over the series, and Ciri helps them to do that. There's nothing that she wouldn't do for them (Ciri/Geralt), and yet they still don't like her, still thinking her of this one-note cruel bitch because of her early appearances (even then she wasn't that bad). Did we read the same series? I can't help but think they weren't paying attention and decided not to bother paying attention due to one bad thing she did and that was it, because how could you think she was a terrible person after reading the whole damn book series? Yennefer is an amazing character, one of the best in the series and a heavily flawed one, that most simply see, turn their nose at and disregard her, despite literally everything else she does. She was made to break the generic fantasy love interest, and she did that, I'd say. It made her a better character, not the easily disregarded lover of the main character; she can stand on her own.
Both women are cool and amazing, neither have done good things and could probably improve aspects of their behaviour, but again that's a flaw that EVERYONE in the witcher has. I'm just happy to reunite Geralt and Yennefer again, they both deserve it <3 Triss can go to Kovir with her mage buddies and rock politics.