Depends on the make honestly. I noticed once that a lower odometer car was more expensive compared to a newer car of the same make. So given they are the same model, I'd choose the one with lower odometer read if it were still in my budget.

Also 2016-2018 is old enough you can probably research to find out what the common issues for them are, if they had any recalls etc.

Your first question should be: does it run reliably? Check the repair records and you want to see regularly maintenance, what was repaired, and how long ago. If the owner doesn't have anything, walk away unless you're willing to pay a mechanic to check the car over. Even then, it's a blind shot.