It is almost certainly based on the Cortex A9 instead of the A8 that current Snapdragons use, which means multiple cores. Apple knows how to use multiple cores effectively and the ability to stop them when not using them is a nice power savings.<p>Snapdragons extend by adding in the wireless circuitry. I'd wager that A4 left that to other chips and extended with someone's graphic rendering engine, say Imagination Technologies?<p>But I think the most important reason is that it lets Apple make the design decisions that make sense for <i>their</i> projected use, not what some chip house thinks will be the focus three years down the road.