Bigfoot beats Mir. Mir probably won't be able to get powerful submissions like a kimura in because Bigfoot is so heavy on top of you and it would be so hard to control his arms like that. He might hit with a triangle but that was never his style. A guillotine isnt out of the question either, but this is all if Bigfoot decides to go to the ground (where he is a very talented BJJ fighter), but he'll probably keep it standing. He'd out power Mir against the cage so the Cro Cop performance is out of the question and I think he'd have too much power for Mir to withstand on the feet. Mir would have to pull guard and pull something off as he does.
I'm probably the best at keeping threads on topic of all time.