Over the past couple of days, reports have been spreading that suggest iPhone 6s and 6s Plus smartphones that use a Samsung-made Apple A9 SoC feature worse battery life than devices that contain a TSMC-made A9. The discrepancy has reportedly been as large as 2 hours in GeekBench's battery test, which is pretty significant for two devices that are supposed to be identical
According to Apple, though, the differences in SoCs produced by TSMC and Samsung are nothing to worry about. In a statement regarding the matter, an Apple spokesperson said that the "actual battery life" of the iPhone 6s line varies "within just 2 to 3 percent of each other... even taking into account variable component differences".
The company went on to suggest that the battery life figures reported by some "are not representative of real-world usage," since the benchmarks are too processor heavy and "misleading" to measure real-world battery usage. In short, according to Apple, consumers shouldn't worry about whether their iPhone comes with a TSMC or Samsung SoC.
While the testing done by third parties does suggest TSMC A9s are better than Samsung A9s, it would be unusual for Apple to approve two SoC manufacturers if they produced chips that were significantly different. On top of that, the tests that have been performed are only a small sample (usually just a handful of devices) of the overall iPhone 6s population, so they don't necessarily indicate a wider issue with some A9s.
This leads us to believe that Apple is correct in saying the discrepancy in battery life is not significant, although new tests performed on a much larger sample of iPhones may indicate otherwise, as Apple does have a vested interest in getting people to purchase new iPhones and not return those with Samsung A9s inside.