Android has eclipsed iOS in efficiency.
I can tell you this much with surety, a nexus S running CM 11 is without a doubt smoother and faster than iPhone 4 running iOS 7. KitKat is just a crazy update, you could really not do much with 512 MB ram phones running any version of Jelly Bean. But now suddenly games run smoothly and you can multi task without apps crashing its really amazing.
Now I know I know none of the old 512 MB phones actually got official updates so that is an entirely different matter. But hey we have got CM and they have done a fantastic job on older phones. It shows that Google wasn't just talking BS when they talked about KitKat being lighter. And it also shows again the big advantage of open source and that Android at its heart remains open source.
So what a shame this truly is for Apple!! Android still has many more features than iOS and yet it seems less resource intensive now. Who would have thought this day will come?