Personal experience ..
IPhone 4 - running IOS 6 - really great battery life, more than a days worth. Never run out. One of the many, but a main reason I use Iphones and not Android phones.
IPhone 5C - running IOS 7 - much worse than the iphone 4 running the previous OS. This is with all the settings, bluetooth, graphics settings and background app location refresh set to OFF, and other recommendations to save battery life.
IPhone 5S - running IOS7 - seems a little better than the 5C so far, but to be honest, hard to tell for certain right now, I've only used it for a day.
My observations - The better processors and graphics cards on the new phones, will require more energy. And IOS7, which is clearly a more demanding, graphic intensive OS will also require more. So even though the batteries on the new phones have been improved in terms of capacity, this gets very quickly swallowed up by the hardware and software demands. And battery life very sadly, doesn't seem to be the main priority for Apple or any other smartphone manufacturer.
For these reasons, at this point I'm thinking that its unlikely I'm going to get the same kind of battery life I got with my iphone 4.