I would go for the ultrasonic one, they are much more reliable.
However they are nether very suitable for what you want. It says on the website about the ultrasonic one:-
Objects from 0 inches to 6-inches range as 6-inches.
Is this one line/beam that it shoots out or like a sonar (depthfinder) cone angle?
They are all cone angle ones, the only straight line one would involve a laser.
Also installing stuff in a car is tricky because of the interference on the power supply.