If we're really counting this shit then Jinha had way more instances of bitchiness and most of Siwon's bitchy moments were just a reaction to Jinha's.
But really, who acted like a bitch is beside the point. What really mattered was whether or not the characters were willing to talk it out. Jinha is only focusing on himself, he has been this whole time. He doesn't care what Siwon has to say unless it's something along the lines of "I love you." He wouldn't accept any other ending, even if that meant making Siwon suffer. Siwon however, just wanted to make things right. Seeing Jinha practice self destructive behavior hurt Siwon as much as losing his childhood friend did.
It isn't even close to a tie.

Jinha is terrible. He'll only listen to Siwon if it results in a happy ending for himself. Everything works out since Siwon has romantic feelings for Jinha, but if he hadn't, Like a little bitch, Jinha would rob Siwon of any closure because if he can't be happy then neither can Siwon. No matter how hard Siwon tried to make up with him! (After all Jinha put him through, he's lucky Siwon was still trying to make things right) That's just fucked up.