This distinction is very important, for up to 75% of pregnancies end in miscarriages (the 75% figure includes cases where the fertilized egg does not implant in the uterus, but if we're using the 'potential life' argument this counts, as everything from a fertilized egg onwards is a 'potential' life).
If one still claims that a potential life has a similar moral status to an actual life, then the same applies for potential good and potential evil. We can then arrest people for crimes they have not yet committed, and lavishly reward people who have not yet performed praiseworthy deeds.
Of course this doesn't work with people who claim that a fertilised egg is as much of a life as a living, breathing human being, but then Faith is immutable to Reason (the same might be said about the 'potential' life argument, but at least that can be challenged by rephrasing it on secular grounds). We could profitably get those who make this argument to endorse some forms of genocide, though (fertilized eggs are alive -> most
Incidentally, one of the ways to reconcile God's Omniscience with Free Will is Open Theism - God knows only probabilities about the future, so we still have Free Will. Yet, if a potential life is similar to a real life, so too is a probable future similar to a real (actualised) future. So Free Will does not exist.
