I've only just finished Book 4, so maybe I will change my mind eventually, but so far it's been a solid #SoKeefe for me. I was neutral in Book 1 and even leaned toward Fitz a little, but starting Book 2 I started to really consider SoKeefe as the more satisfying endgame, for the following reasons:
1) As a commenter on the KOTLC website has noted, Sophitz just feels too... immediate. Like in literally the first chapter, Sophie already has a crush on him, and I remember thinking "Okay, so this is the leading man. They'll end up together eventually." even before I knew anything about Fitz or the kind of relationship he would have with Sophie. Ending with them together despite the availability of other viable love interests feels just... flat... for me. Meanwhile, Keefe started out as the annoying dude that Sophie didn't really see in a romantic way, and then their relationship just evolved. It's a lot more realistic and satisfying if they end up together.
2) The "love" Sophie feels for Fitz is always just described, but hardly shown. Again, maybe this won't be the case in the books I have yet to read, but in the first 4 books, I definitely had this sense that story is "telling" more than "showing" when it came to Sophitz.
Consider this- how do we know Sophie likes Fitz? Because she always says/thinks so. On the other hand, how do we even get the notion that Sophie likes Keefe? Beause she acts like it, even without realizing it. One thing that really stood out to me in Book 4 was when they were in the healing tent in Exillium, and Sophie learned that Keefe kissed Biana, and she didn't *think* or *say*Ā that she was jealous or anything, but she couldn't understand why her fists were suddenly clenched so tightly. This is in super stark contrast with almost all Fitz scenes where we are *told* that her heart flutters and she *knows* it's because he's smiling / looking at / complimenting her.
3) The relationship between Sophie and Fitz almost seems forced. Again, I've ony read up to Book 4 so maybe this will change, but it seems to me like they only ever spend time together and their relationship only grows because of necessity. Fitz found her because it was his job. They do trust exercises because they're Cognates, and the fact that Fitz is the only other Telepath in their group of friends kind of weakens the argument on 'special connection'. I mean, who else is there as an option for a Cognate? Who else will she have a 'special connection' with, when there's no one else withĀ the same ability as hers?Ā Meanwhile, Keefe and Sophie's relationship grows tremendously because of their choicesĀ instead of what they need to do, which makes it a lot more meaningful than the 'forced' interactions between Sophie and Fitz.
A very big example here to mark the difference is when Fitz was depressed in Book 2, he shut Sophie out and to be honest, she didn't do anything much to get him to accept her help. Meanwhile in Book 4, Sophie *actively* tried to push into Keefe's solitary bubble when he was depressed and doing serial killer things in his room, and he too choseĀ to be receptive, even after he became mad at her for hiding things. They didn't need to do that, honestly. The peace of the elvin world did not hinge on Sophie and Keefe's friendship continuing as much as it did Sophie and Fitz learning to work as Cognates.Ā Sophie could have left Keefe to Fitz, the best friend. Or Keefe could have chosen to stay mad. But they worked it out and stayed friends, even without the prodding of necessity.
This is also the case when they are not in trouble (as much as they can be not in trouble). Keefe actively pursues a friendhsip with Sophie, but Fitz, not so much. He seriously receded from prominence in the books after Book 1 (but then again maybe I'm just not updated and this will change in Book 5, but seriously, what message does it say that Keefe *has* to be out of the picture before any real progress can be made between Sophie and Fitz?), while Keefe has entire arcs dedicated to him.