As someone who read the webtoon before watching the drama, I have to say Team Seojun. It's kinda heartbreaking that we didn't get to see Jukyeong and his relationship in the drama, when it was so beautiful and blossoming in the webtoon.
There was a whole side to Jukyeong that we never got to see, and that's just really, really sad. The drama didn't do her justice, in any way, shape, or form. Jukyeong in the drama is all too different from the one in the webtoon, and even just reading very few chapters of it, it'll be clear to anyone, just how different they are. And with Seojun too. He wasn't that mean bully you might think he is, from watching the drama; he is just the kindest, towards Jukyeong at least, of them all.
Anyway, Team Jukyeong x Seojun for life.