We had an article when Pro came out which I think will be the good source to find out the differences between X and Pro:
But the ultimate difference can be found in the tutorials. Kindly read this article to know the power of the Pro:
Pro is intended for more savvy customers which needs flexibility and don't afraid of having too many options. It has a steeper learning curve than X but as soon as you get the hang of it you will see the vast possibilities you have in your hand.