I think part of that was that the graphics layer on the iPhone was GPU accelerated from the start, and the first few versions of OSX were not. One of the thing

I think part of that was that the graphics layer on the iPhone was GPU accelerated from the start, and the first few versions of OSX were not. One of the things that Microsoft got right and Google got wrong was that Microsoft copied the concept of using GPU accelerated graphics with Windows Phone and it took Google quite some time to catch up.