Well, it depends how many miles you drive a year. If it's a relatively low amount, I'd probably go with the one that's a little higher miles, since at the end you still won't be killed in miles. If you drive a lot - let's say more than 20k miles per year - then you need to go as low as you can on the miles.
Personally, I would choose neither option and save and buy a vehicle for cash, even if it wasn't a Titan. That said, if you have to make payments either way, how much are the payments? You might just be a candidate for a new vehicle if you're going to be making payments for 5 years anyway. In my mind, there's no real sense on spending 5 years paying off a vehicle that's already several years old, if the payment amounts are nearly the same. Unless of course you drive ridiculous amounts of miles.
Car payments are evil things, man.

If you have no real alternative, and the payment amount is the same, get the newest, lowest miles you can afford. That might just be something that's brand new. There is almost nothing worse than making payments on a vehicle that's broken down or killed in miles. At least if you're making payments on a new truck, and you don't kill it in miles, you have something at the end other than a wore-out vehicle.