In the obvious way that the iPad4 has the A6
The mini will get the A6 too once they add the Retina screen, but it
IS a difference which is what you asked for.
I agree with you, and as I said before, I think screen and processor aside, the mini is the real winner.
If you're referring to the new shape then this is no small thing. Hold both in your hands for 30 minutes and you'll soon see that the iPad4 feels more awkward and the mini still feels completely natural. Apple did a great job with the minis shape. I see this as a big improvement over the full sized tablet, which was already good. The mini is hands down the most comfortable tablet on the market.