The biggest advantage of the pivot compared to the px is that the pivot would not slide back and release when landing switch, like a standard track binding does. The increases forward pressure on the px addresses this to some degree, but will still slide back under hard impact.
The px releases more consistantly from all angles which makes it slightly safer. It is all about trade offs and prefferances, but the only way to make good educated choices is to get out there and ride different equipment. Then you will know what you like and you don't.
And remember, nothing is perfect. The FKS bindings for instance dont release upward (except 120), and wing solly's prerelease if not adjusted properly and rechecked daily.