Android's share rises as new phones are introduced, and over time it continues to gain share, because its phones cost less. But when the product introduction front is quiet, Apple quietly takes some share back.
The reason, I think, comes down to two words: battery life. Apple cares about it.
The folks at iFixit have done teardowns on both the iPhone 5, which many friends already own, and the Google Nexus 4 , which I own. Both have specialized Qualcomm power management chips. Most iPhone chips are on two sides of a single logic board, while those on the Nexus cover a larger, L-shaped board.
Last year's iPhone 5 uses a solid Lithium-ion battery that runs at 3.8 volts and has 1440 milli-amperes/hour (mAh) of charge. The more mAh in a battery, the longer it will usually take to discharge. The power drain is listed on the iPhone battery at 5.45 watt-hours (wH).
But it doesn't.
There are three main causes for a phone's data battery drain the Global Positioning System module, which knows where you are; the WiFi module, whose radio rains data when you're near a hotspot; and software, especially multi-tasking, keeping several programs running at once.
The GPS is the biggest energy hog. My first Android, a Galaxy 2, would drain the battery on GPS even when plugged-in to my 6 Volt car battery, making it useless. The Nexus 4 is a little better, but you still need to plug it in when you're seeking directions unplugged mine runs for under two hours on GPS.