>"When you program for Android/IOS how much of the logic you write is referenced from optimized libraries and how much is your own craft?"
It doesn't matter either way.
For one, Apple and Google aren't that keen on optimising their stuff either.
Second, most desktop applications use libraries and GUI toolkits by a major source, like Apple and MS, so the situation regarding "a large part of the app is made by a third party that can optimise it" is there for those too.
Third, tons of iOS/Android apps use third party frameworks, like Corona, MonoTouch, Titanium, Unity, etc etc, and not the core iOS/Android framework.
Fourth, the most speed critical parts of an app are generally the dedicated stuff it does, and not the generic iOS/Android provided infrastructure code it uses.
It doesn't matter either way.
For one, Apple and Google aren't that keen on optimising their stuff either.
Second, most desktop applications use libraries and GUI toolkits by a major source, like Apple and MS, so the situation regarding "a large part of the app is made by a third party that can optimise it" is there for those too.
Third, tons of iOS/Android apps use third party frameworks, like Corona, MonoTouch, Titanium, Unity, etc etc, and not the core iOS/Android framework.
Fourth, the most speed critical parts of an app are generally the dedicated stuff it does, and not the generic iOS/Android provided infrastructure code it uses.