A recent benchmark report by Ars Technica suggests that the TSMC A9 chip based iPhone 6s delivers almost two hours longer battery-life than its Samsung counterpart. In response to such reports, Apple has claimed that the difference in real world usage is barely 2-3%.
The various benchmark scores conclude that the Samsung system-on-a-chip (SoC), yielded consistently lower battery life results, in comparison to the TSMC chip in the iPhone 6s, with the exception of WebGL test where the former overtook the latter. The scores have been computed based on a variety of tests including Wi-Fi browsing, WebGL, Geekbench 3, and GFXBench tests.
The report also emphasises the fact that the Geekbench test is the one that makes a significant difference in the overall result, which is attributed to the "SoC rather than the screen or the battery itself or some other system component".
Explaining the limitations of the test, here is what Ars Technica had to say:
It should be noted that no matter how many variables we try to control for, any testing of a sample size this small can only tell us so much about a problem that's this complex. Our two iPhones have different A9 SoCs, but we don't know what else differs between them—Apple uses multiple sources for many components, including displays, RAM and NAND, and even things like the Taptic Engine.
Others with Samsung and TSMC phones to compare have also found differences that largely echo our findings, which makes us inclined to believe that there is a difference between the two, but even if you add up every test from Reddit and Apple fansite forums and the Geekbench database you still get just a fraction of the 13-million-plus iPhone 6S and 6S Plus models that are already out there in the wild.
Apple is the only entity that can even come close to providing a sample large enough to be representative, and while it says that the differences between all models (not just Samsung-vs-TSMC, but all phones with all components) average out to 2 or 3 percent in "real-world usage," though the company wouldn't tell us how it makes that determination or what its internal battery life testing procedures are like.
So, we think our data is as good as it can be given our sample size, and our findings seem to confirm what both independent testing and Apple's own numbers are saying. But this also isn't the last word on the whole Samsung-vs-TSMC situation, and our understanding of the problem will continue to change as more people run more tests and as more chips and phones are manufactured.