You're saying their lack of feature was a feature. It's like saying my Nokia 5100 is so power efficient than your smartphone that it's better. Different intentions.
It's a lot harder to leave out features than adding. You have to be carefull about what you leave out, make sure you don't touch core-functionality, and make sure the features that are present are done brilliantly, because they will be in the spotlight, all the time. I'm not saying Apple does this flawlessly, I'm not a blind fanboy, they have serious misses (notifications pre-IOS5, Calendar app, IOS folders, ...) - but they do this a lot better than anyone else.
To be honest, I never had problems with "missing" features (except calendar/call overview in the lock screen), but more problems with the implementation of features that were present, but not executed well enough.
They deliberately limited functionality to provide a feature. They then provided more functionality which removed some of those original limitations.
Power efficiency has nothing to do with it in the slightest.