Apple’s statement regarding the iPhone 6s battery life kerfuffle, as published by TechCrunch:
With the Apple-designed A9 chip in your iPhone 6s or iPhone 6s Plus, you are getting the most advanced smartphone chip in the world. Every chip we ship meets Apple’s highest standards for providing incredible performance and deliver great battery life, regardless of iPhone 6s capacity, color, or model.
Certain manufactured lab tests which run the processors with a continuous heavy workload until the battery depletes are not representative of real-world usage, since they spend an unrealistic amount of time at the highest CPU performance state. It’s a misleading way to measure real-world battery life. Our testing and customer data show the actual battery life of the iPhone 6s and iPhone 6s Plus, even taking into account variable component differences, vary within just 2-3% of each other.
I checked my iPhone 6s a couple of days ago with Lirum Device Info Lite and found that I do have the Samsung-manufactured A9 chip. And although I’m only a single data point, I’ve been more than happy with my device’s battery life. If you’re experiencing battery life that seems outside of Apple’s range of acceptability, my suggestion is to take your iPhone to your local Genius Bar and try to get a replacement.