Like everyone has basically said already, it's JDS if we're hypothetically talking about a boxing/kickboxing match. I wouldn't count Cain out of it completely, but while they have comparable handspeed, JDS has the better chin to afford more mistakes and honestly probably better utilization of footwork.
When you introduce the threat of takedowns, it's another story.
I have to wonder how much of a toll those body shots JDS absorbed took on his cardio too though, and not just the chain wrestling. Really brilliant display by Cain.
Anyways, I still see this as anyone's fight when they meet again, and I don't see anyone other than Cormier giving JDS similar problems. JDS has Overeem's number. Heck so does Cain for the exact same reasons we just saw last Saturday.