I confused the two screenshots. I'm terrible with graphics comparisons. I tend to think graphics are great if the game is great, even if the graphics are comparatively terrible.
"To have "retina display" on iPad-size screen, you have to replace each pixel with a 3x3 pixels matrix of the same size, so you will have 9x more pixels on hypothetical iPad retina display. And - surprise! - iPad 2 graphics power is exactly 9x more than iPad 1. So, basically, iPad 2 is already capable of running retina display, though with the same speed as iPad 1."
That's what I think the performance upgrades to iPad 2 in fact are: a head start for developers to produce software that can take full advantage of a retina display in iPad 3, so there will be a software base already in place that runs on iPad 1 and iPad 2, but will immediately show off the enhancements of a retina display in iPad 3. Apple could have merely added the cameras and associated software, put iPad 1 on a diet as they did, and they'd still sold like crazy. The overwhelming majority of customers won't know or care about the performance improvements. But since Apple holds everything so close to the vest until announcement, developers can't work on iPad 3-ready versions of their apps w/o something similar in performance specs already on the market. Thus, iPad 2 has the performance architecture, more or less, of iPad 3.