I would think most ball and coupler failures are user error. Forgetting to latch the coupler happens often, and I bet many trailer users have never adjusted the coupler itself. As long as you have quality components and use them properly, you shouldn't have any issues with either style connection.
If you can read this, thank a teacher. If you can read it while pooping, thank Bill Gates!
"A girls butt hole is like a 9 volt battery. You know its wrong, but eventually you put your tongue on it."