Who would you rather trade? It's actually tougher than I thought because of Smyly's durability issues. With Porcello, you know he'll log bout 175-180 innings a season. Another thing that comes into factor is the return we get back in a trade. You would assume Smyly would get a better return because of control and his stuff but again, he has a hard time staying healthy whereas Porcello hasn't had a significant injury his entire career.
Edit: Forgot to answer my own question. I'd trade Porcello.