The biggest beef that people will have with the iPad Mini (other than price, that is) is that it doesn't come with a pixel dense Retina Display. It's the only new iOS device — iPad 4, iPhone 5, iPod Touch — that doesn't have one. But it turns out, its screen is still much better than the iPad 2 because its pixels are smaller.
Repair Labs put every iPad screen under the microscope to compare pixel size and found that though iPad 1 and iPad 2 have the same pixel size (and iPad 3 and iPad 4 have the same), the iPad Mini's pixels are much smaller. And when compared to the Retina Display iPads, the iPad Mini's pixels aren't that much bigger. Repair Labs says:
The iPad mini is where things get interesting. Its smaller size necessitates a few sacrifices and the Retina Display (at this point) simply cannot be made to fit the new small chassis, so to speak. But lo! The difference between the 4th Gen and the mini is not that huge when examined under the microscope. In fact, the pixels of the Retina Display are only 2/3 the size of the iPad mini. In the older iterations, the pixels of the 4th Gen are ½ the size of the older versions, or .50. Here, they're a full 16 per cent (.16, since the 4th Gen's pixels are 1/3 or .66 of the size of the mini) larger in comparison. This means the difference between the two, is less noticeable. In fact, to the naked eye, it's negligible. Why is this? Since it's a smaller screen, the pixels are packed much more densely.