Jesus fanboys are annoying - a bigger battery, all other things being equal will last longer. It's very simple science.
It's only people who sit on sites like this all day and wear Apple logo pyjamas who excuse everything Apple do as being better. If Samsung designed the proposed iPhone 6 they would be mocked for the thick bands and protruding camera, small battery, low RAM etc etc.
Everyone I know with a mobile phone would like better battery life, no-one I know has said they want a thinner phone. It doesn't matter what optimisation the A8 chip has - when you sit staring at the screen the battery will be eaten, the 5.5 will no doubt be fine but the small battery in the 4.7 will be struggling.
Wouldn't a bigger screen and higher res and more powerful processor to power than high res drain more battery.