I always felt like there was something I was missing about the “sorry but I’d rather have you” speech in 7x23. Now I think I’ve figured out what it is.
As a reminder, Dean says to Cas:
Cas: I’m not good luck, Dean.
Dean: Yeah, but you know what? Bottom of the ninth, and you’re the only guy left on the bench… Sorry, but I’d rather have you, cursed or not. And anyway, nut up, all right? We’re all cursed.
This directly echoes a scene that takes place in 5x18, “Point of No Return”. Sam and Bobby have locked Dean (who’s threatening to say yes to Michael) in the Panic Room, when Sam comes in to let him loose. They have the following conversation:
Sam: There are too many of them. We can’t do it alone. And uh, you’re pretty much the only game in town.
Dean: Isn’t that a bad idea?
Sam: Cas and Bobby think so. I’m not so sure.
Dean: Well, they’re right. Because either it’s a trap to get me there to make me say yes, or it’s not a trap and I’m gonna say yes anyway. And I will. I’ll do it. Fair warning.
Sam: No, you won’t. When push comes to shove, you’ll make the right call.
Dean: You know, if tables were turned…I’d let you rot in here. Hell, I have let you rot in here.
Sam: Yeah, well…I guess I’m not that smart.
Dean: I don’t get it. Sam, why are you doing this?
Sam: Because… you’re still my big brother.
So basically, when Dean says to Cas “I’d rather have you, cursed or not”, he is explicitly recalling the conversation he had with Sam in 5x18. It’s a parallel so obvious I’m shocked I never noticed it before.
The words Dean says in that barn sound desperate, like he has nothing left to lose in trusting Cas, but that’s not it, not at all. “I’d rather have you” is, in Winchester-speak, about Dean demonstrating the deepest faith in Cas, the faith that he only reserves for family, the faith that no matter what has happened between them, he still believes Cas will make the right call.
Why? Because Cas is still family. Because Cas is still Cas.