It's not the pros and cons that stops Jesse. No, it's the break in Pinkman's voice. It's the desperate tone, and Jesse's not sure exactly what to think. The nightmare could be really fantastic at acting, but Jesse doesn't remember it being so. It'd take memories. Use them against you. But Jesse doesn't know Pinkman very well. Doesn't have memories of him at all, really. So why would the nightmare use him?

Jesse pauses, and bites his lip, hand faltering. He looks weary.

For a moment, he's quiet, and then he looks down at the glass. Keeps it there, but his hand is shaking, hesitant. He really, really doesn't want to do it, but if it was the only way...

"Pros're I get to wake up," Jesse says, finally. "Cons, I die for real if - if I ain't..." He wavers - and it pours out in a rush: "I dunno. I dunno what t'do. I should. M'scared."