I've got a question about if you own the iPhone 4 today, what to buy, the iPhone 5 or the Samsung Galaxy S4? I would say, none of them.
If you still want a simple phone that just works and without customizations and user choice, then stay with the iPhone, but wait for the iPhone 5S that will be released this Fall.
Or if you want a more fun and exciting experience, then switch to Android, but buy the recently announced Samsung Galaxy S4 Active instead of the normal S4. Or why not buy the HTC One? It has the same build quality as the iPhone but is running Android.
So that is my recommendation.