Only locks I have had fail are the Dunlop type, fortunately I have always caught the bass. Hardly surprising, giving the design! The idea of everything resting on that one pin freaks me out completely.
Schaller design certainly makes the most sense, with the lock fitting over the button, as opposed to on top. Keeps the bass closer to the strap as well and comfier as a result. Tighten the nut on the strap properly (ask someone strong if you need to...) and it won't come loose, just as many things tightened with nuts don't come loose! Rotation arguement is bizzare as the lock fitting should not rotate at all, if it is then you are doing it wrong and it's no surprise it loosens! Using the same logic, why aren't our tuners falling off our headstock all the time
But, I don't use either. I use grolsch washers. Why? Never failed and for all my pulling and swinging around I can't see how they would in normal use.