Shu Yi is my favorite character. I love his passion, his resolve, his justifiable fury at having been so shabbily treated. Going back to S1, I love that he took himself through the soul-searching and intellectual self-examination required to get to where he allowed himself to return the love he was receiving from Sam. Or perhaps more accurately, to accept and embrace the part of him that already loved Sam despite the fact that apparently to this point in his life he thought of himself as strictly straight. I love that on the bridge, during the confession scene, he took the initiative and talked Sam through HIS BS that was refusing to accept what he had wanted for so long. I love that he stood on the bridge railing and shouted his love for Sam to the world. I also loved when he slapped the shit out of Shi De when they first re-met.
I think I like Shu Yi for the simple reason that I identify with him strongly. Put in the same situation, I would likely be responding in much the same way. I feel I understand him. I am probably well in the minority here, but I am actually pulling for Shu Yi to NOT forgive Shi De and to not reconcile with him. I want him to move on and find a wonderful man or woman deserving of his love. If I were treated as Shi De treated Shu Yi, I would never be able to trust that person again. It really doesn't matter what excuse they come up with for Shi De not to contact Shu Yi for five years, the fact remains that he agreed to it and didn't consult with Shu Yi and tell him what was going on, which could have been done secretly in a number of ways, given today's technology.
I dislike BL characters who make huge life-changing choices for the couple, regardless of their reasoning, without consulting their partner. It's an unforgivable abuse of trust and very cruel.
Sam may be the better actor at this point, but the script has him playing such a walled-off, arrogant jerk that it seems more like a stock character than an individual human being, so for me it's hard to evaluate the performance. It's easy to play an arrogant jerk.