We have 4 Shield's, 2-9's and 2-40's. One each of the 9 and 40 are PC's. We don't notice any flash from the porting when we shoot the guns, and the porting helps a little bit with the time to get back on target, but I would not call the difference huge there.
The bigger pluses of the PC version, at least to me, are the trigger and the fiber optic sights. We both really notice the trigger when going from the non-PC to the PC versions. Less creep and more crisp.
They all shoot well, but I think the PC version is for sure worth the extra money.