^^^These
Same reason the iPhones can get away with using dinky 1400 and 1500mAh batteries and still last longer than "other" handsets with 50 to 100% larger batteries. Software optimization goes a long way in using what hardware the device has, more efficiently.
Look at it this way: The iPhone 5S only has a 1.3gHZ dual core processor and only 1gb of RAM... yet, when you put it up against devices that come loaded for bear, like the 2.2gHZ quad core 2gb RAM LG G2, or the 1.9gHZ quad core 2gb RAM Galaxy S4, the iPhone 5S bests them both in benchmarks across the board.
*Disclaimer: I am not saying that benchmarks matter. I believe end user experience is far more important... and in that regard, I don't believe Apple has ever trailed a competitor, no matter what the benchmarks say.