What is the difference between 12x50 and 18x75 differential gear sets?

The gear ratio of both 12×50 and 18×75 is 4.166666666666667 which is the same.
But why don’t car manufacturers use only one of them while the ratio is exactly the same?

My only guess is that when the number of teeth are lower, the gears are stronger (can withstand more torque) but they are noisier.

Can someone please shed some more light on this?