chino, wow. I think that's pretty darn close. Except that I think Yukio would believe that Rin could learn to control himself. He thinks Rin is perfect, after all. Yukio doesn't believe he can do that because he's defective.
Honestly, I'm also conflicted on what romance is better. I like both YukiShu and YukiShie for different reasons. It's hard to say how Yukio will turn out by the end of all this. Shura's and Shiemi's development is much easier to predict. Shiemi is getting stronger, more forthright, but also less self-centered, like how Rin is learning. (I really do like chino's point about how Shiemi and Rin both do nice things because they like to do it, which isn't necessarily a good thing to do all the time.) Shura is catching up on twenty-seven years of only keeping ties she wouldn't mind leaving, so her growth is more reexamining how to live. She's a secondary character though.