Quoted from Tuna_Delight:Power Shifts are the biggest feature that the Pro lacks. The Road Hazard pop-up targets are great risk vs reward shots and having Power Shifts available to help complete a tougher mode and get to Drift is a good thing indeed.
The different colored shot arrows, MUSTANG letter selection, electronic orbit gates, and diverter ramp are nice too.
The cross ramp on the premium is a cool feature. It will divert the ball to the right when a shot needs to be made by the right flipper. I love the game. It's a good mix with games like TWD, ST and GOT, in my opinion.
Here's the feature matrix that gives you the differences: http://www.sternpinball.com/upload/games/mustang/premium/Mustang%20Pinball%20Matrix.pdf