I don’t care what the salesman promises, always have a used vehicle inspected thoroughly by a professional mechanic, before you purchase the vehicle. 

You don’t want to realize after you’ve purchased the vehicle, that the salesman lied about the CPO claim, or the CPO inspector missed some major items.

Get it inspected by someone you trust before you give them your hard earned money!

That’s just another thing dealers do to make you pay more money. I don’t even trust it. Whatever you decide to buy, take your own mechanic to check the car. With that said, do not fall for the CPO trap. 

At car dealerships the standard way of doing business is to get you to buy a "certified" vehicle, or sell you and extended warranty.  Then when something goes wrong, they tell you "That's just the way it is and there is nothing we can do about it." 

back in the day, you checked the horse's teeth yourself. "Honest" Mr. Dealer will sell you anything.

I would go with the non-certified one, assuming it passes your own independent, honest mechanic’s inspection.

With certified pre-owned (CPO) you are paying extra and the dealers sometimes don’t do all the multiple-point checks they are supposed to (I noticed on numerous occasions on the CPO cars I was looking at that there were leaks and other issues - no coolant in reservoir tank! - that they clearly missed.)  Even with CPO cars, you still want an independent, honest mechanic to check out before you buy because you can’t trust these dealers.

It depends on the dealer but a lot of them just slap the certified label on it and jack up the price. I wouldn't pay more for a "certified" car.

I would buy the cheaper, lower-mileage one. Whatever you buy, have it inspected by a independent party.