The news coming out this week is that this Ranger (which is actually an older truck) is only going to be on sale for another 24 to 36 months. The all-new Ranger will share it's platform with the all-new Bronco in 2021.
SO... taking that into consideration I would personally try to get the biggest discount possible on the 2019 model so that you hopefully won't have negative equity in the truck for the life of the loan.
Obviously if you're planning to keep the truck forever then none of this matters.