There was never a Google Maps app on the iPhone, there was an Apple app powered by Google's data.
The correct way of stating this is that Apple's iOS6 maps app is more data efficient than previous versions. As for the main reason the current app is more efficient is that it relies on vector graphics instead of image tiles, a technique Google have been using on Android for nearly 2 years:
http://googlemobile.blogspot.com/2010/12/under-hood-of-googl...
There was never a Google Maps app on the iPhone, there was an Apple app powered by Google's data.
The correct way of stating this is that Apple's iOS6 maps app is more data efficient than previous versions. As for the main reason the current app is more efficient is that it relies on vector graphics instead of image tiles, a technique Google have been using on Android for nearly 2 years: http://googlemobile.blogspot.com/2010/12/under-hood-of-googl...
Another Android maps feature lets users select areas to cache offline, which I imagine saves even more data (it auto-caches frequented areas): http://google-latlong.blogspot.com/2012/06/go-offline-with-g...
That feature is also worth mentioning for when Apple duplicates it and some people try to convince themselves that it was Apple's idea.