Not all iPads are made equal, even if they're all packaged and branded identically. There's a major new mutation within the 2nd generation tablet and it brings significantly better battery life. Specifically, the fourth and latest production model of the iPad 2 (known as iPad2,4) has not only a lower price tag ($399) but also a new 32nm processor, which is significantly smaller and more efficient than those in previous iPad 2s (which had 45nm chips and an older transistor design). According to AnandTech, this results in an overall 16 percent increase in battery life during web browsing and as much as a 30 percent boost when playing games. Obviously that's worth having, but how can you tell if a boxed-up iPad 2 has the new processor before taking it to the checkout? Here's the downer: you can't. Until retailers' inventories naturally flood with the updated type, the only way to tell is by switching the slate on and running a utility like GeekBench -- and perhaps there'll be circumstances where you can give that a go on the shop floor. Alternatively, if third-party sellers discover that their stock is the iPad2,4, they could pull off a Darwinian win-win by marketing that fact to buyers.