Postby davew » Wed Aug 07, 2013 11:02 am
Short version...
iPad 1 < iPad 2 < iPad3 = iPad Mini < iPad 4 (iPad 4 is the current retina iPad)
Long version...
The mini sits between iPad 2 and 4 in performance terms. It has the double resolution "retina" screen so it displays the same "pixels" as an iPad 2 but in half the screen area, giving a really good image quality.
The iPad 4 has Retina too so has double the screen resolution of the iPad 2 as well as double the screen area of the iPad Mini. the only limitation of the Mini is it's screen size really, for web browsing, map viewing etc... it's nice to have the extra screen area of the iPad.
The iPad 3 was only around for a relatively short time, being replaced with the iPad 4 when the iPad mini was launched. The iPad Mini came in at around the same performance spec as the iPad 3, albeit with a slightly reduced graphics processor - presumably because it only has to handle half the pixels so doesn't impact performance.
iPad 4 is probably around a 20% increase in performance over an iPad3/Mini with extra RAM. The iPad 3 and Mini use a dual core 1000MHz ARM CPU whereas the iPad 4 uses a dual core 1400MHz Apple Swift CPU and a slightly upgraded quad core graphics CPU over the iPad 3.
Apple have a rolling obsolescence program for their iOS devices which means that new releases of the operating system won't work on devices more than 3 generations old. It's worth bearing that in mind when buying second hand as the free major operating system upgrades that are released each year only support devices within their "useful life". This allows the operating system to move forward without trying to support legacy hardware that would compromise it's speed/function.
That means that the iPad 1 is not supported in iOS 7 - the new release of the operating system that's due out in a couple of months. iPad 2 IS supported in iOS 7. It's not a problem as you can continue using the current iOS and apps but you may find as time goes on that you can't install new versions of apps that are designed and targeted to use new features in the operating system.
It's worth bearing the above in mind if buying second hand as it is likely to see "bargains" appearing when users realise that they can't get all the whizzy new shiny functions without upgrading to a newer model. On the plus side you can take advantage of the price drop once iOS 7 is released but on the minus side you won't get all the new features of iOS 7 which, without breaking my NDA, I can tell you, you will want because a lot of new app functionality will be based on the new OS technology.