Why iPad Mini Using 7.9 inch? Before finally deciding to use a screen size of 7.9 inch, Apple apparently has considered a number of screen sizes for the
iPad Mini. There are two reasons and not rational. For those who do not, that the screen size for the iPad Mini, which amounted to 7.9 inches was chosen to allow people to remember that the company has been selling the iPad measuring 9.7 inches. While the real reason is for the selected size is best for a smaller form factor. With a screen size that is smaller and cheaper than the larger iPad,
iPad Mini is ready to 'steal' market share of 7 inch tablets, one of which is
Google's Nexus 7 which is the nearest competitor. Screen size
7.9 inch screen with 4:3 aspect ratio, in addition to much greater than the 7 inch or 4 inch more, also believed to benefit users who want to enjoy the app on the iPad is smaller. Apple also said that the 4:3 ratio is more suitable for tablet experience for users not only to use it with two hands, but an on-menenus also can switch from landscape to portrait orientation.
source
Apple