I believe ball locks have typically been more common. But pin locks are used by a lot of people, too.
I would say the most important thing is to be sure that all of your kegs are the same, so that you don't need different quick disconnects.
There is no specific benefit to either pin or ball lock that I am aware of.
You can't get the in/out mixed up on pin locks.
Ball locks are taller with a smaller diameter (that geometry thing) so more can fit in a keezer.
Pin locks are made out of a thicker gage steel, and are harder to dent, but they are a little heavier.
So there are differences, it is up to someone to decide if that makes a difference.