If you have access to any maintenance history on either of them, buy the one that's been better maintained. Treat your truck right, it'll treat you right. Keep in mind the transmission's aren't invincible on these either, so lower mileage will probably give you more miles on the road before something happens. Mine will break 300k next month and it runs and feels like a car with half its mileage and I have confidence it'll run for as long as I own it. But that's due to a diligent previous owner and me resetting it's maintenance items to "0."