AnandTech has recently uncovered processor difference between the older and newer units of iPad 2. When Apple revealed iPad 3, it also announced that it will be selling iPad 2 alongwith the new iPad at a lower price point of $399. AnandTech performed benchmarks for this newer iPad 2,4 and found out that it features a 32nm A5 processor instead of a 45nm A5. This new processor is far more power efficient than the one found on older versions of iPad 2 and provides up to 1.6 to 3 hours of extra battery life when performing different tasks.
As you can see in the image below, the 32nm A5 chip found on the newer version of iPad 2 is significantly smaller than the 45nm A5 chip.
Due to it’s power efficiency, it is very likely that Apple will use the same 32nm chip in the upcoming iPhone that is expected to feature LTE capability.
AnandTech notes that they got their unit from BestBuy because many Apple Stores are still selling the older version of iPad 2. So if you want to buy an iPad 2 with better battery life, better buy it from BestBuy.