The iPad 4 has an Apple A6X system-on-a-chip (SoC) is marketed as twice as fast, both in central and graphics processing, as the iPad 3 released only 7 short months ago. Apple's custom, manually-set ARM v7s processor -- called Swift -- remains the 32nm CMOS dual-core beast found in the iPhone 5, but it's been cranked up to 1.4 GHz. The X in the iPad 4's A6X once again represents a quad-core graphics processor, this time the PowerVR SGX554MP4. On spec, that's some serious fire-power.
The iPad mini, by contrast, has the same die-shrunk Apple A5 SoC found in the iPad 2. That's a 1GHz dual-core ARM Cortex A9 and PowerVR dual-core SGX543MP2. But the iPad mini also has the same 1024x768 display as the iPad 2. It's smaller but denser, going from 9.7-inches to 7.9 inches, and 132 ppi to 163 ppi, but it's the raw pixel count here that makes the difference.
Retina comes at a price, and that price is performance for the first generation devices that have to support it. The iPad 3, iPhone 4, the iPod touch 4, even the Retina MacBook Pros were and are maxed out trying to push all those pixels. Once that's done, though, once the price has been paid, however, performance improvements go back to where they belong -- making things feel faster.
So, even with the older, less powerful Apple A5, the iPad mini should fly. But will the new A6X help the iPad 4 do likewise?