I like the relief valves better on ball locks However the dimensions on pinlock are better shorter fatter kegs. But if you have your own bottle and disconnects I see no difference
We use both, the pinlocks have a slight advantage in that they are easer to get the right connections on the right posts when your mental capacity is diminished (In a drunken stupor).
I like pin locks better mainly because I never have a hard time getting the disconnects off. Sometimes the ball lock disconnects get stuck if they have been on a while. Plus I can get 6 ball lock in my kegerator but only 5 pin lock. But really it doesn't matter. I only switched from pin to ball because I wasn't able to find pin lock kegs when I was expanding.