fire, I have both the 6.5x20 PA and the 6x24 PST scopes and I like both of them. Both have good ranges for windage and height adjustments as well as parallax adjustments. I have used both of them shooting 308 at 300, 600 and 1000 yards and they both worked well at those distances.
Obviously the PST has 24X magnification, compared to 20X for the PA. The PST also has an illuminated reticle while the PA does not.
Is the PST worth the extra $300 compared to the PA? Not sure, depends on your budget and what you are looking for in the scope.