Interesting. I remember reading before launch that even with the smaller battery, the 6S would have the same battery life as the 6. Now that I've had mine for a week, I've noticed that the battery life is not as good as my 6. I'd like to check with that app. what processor I have, but know I will just end up disappointed at what I find out, especially since you can't just go to Apple and request one with the TSMC chip.
It's like the iPad.
My iPad Air 2 has substantially worse battery life than my iPad 2. They're both still advertised as 10 hours. The Air 2 is awesome, miles better than the iPad 2, but sometimes the battery actually conks out at the end of a day; that never happened with the iPad 2.
I wish I didn't have to worry about the battery full stop.