The phone tear down has revealed and confirmed a few rumours. As we all knew the new iPhone is heavier than the previous generation and a part of the reason is the display assembly which is is now 60 grams, or 15 grams more than with the iPhone 6. Apple had to do this to bring in the 3D touch feature that most Chinese manufactures are going to copy next year.
Apple A9 APL0898 SoC is the heart of the phone. We will still have to wait for someone to Xray the SoC to tell us if this is a 14nm or 16nm chip. The battery is smaller and the iPhone 6S uses a 3.8 V, 6.55 Whr, and 1715 mAh battery. The iPhone 6 had a 1810 mAh battery. The battery size tells you that Apple has made the phone more energy efficient.
Trusted reviews claim that they got 14 hours of mixed use from the phone, which sounds like a lot. The phone can loop video in SD quality for 10 hours. This is less than Galaxy S6 but it is still rather good for such a small battery.
It is good to see that Apple is now using Samsung 2 GB LPDDR4 RAM, and this memory will definitely speed up the multitasking. The tear down revealed Qualcomm MDM9635M LTE Cat. 6 Modem which is not the latest greatest from Qualcomm but it is the best and fastest one for iPhone so far. iPhone 6 is using MDM9625, which is a Category 4 LTE modem, so the new MDM9635M is definitely an upgrade.
There are other chips inside of it, but we won't go into too many details here. iFixIt has a lot of descriptions and pictures to tell that part of the story.
In case you need to repair your iPhone 6S, the battery and display are easy to replace if you are a professional. We are sure that the display assembly will be more expensive with the hew iPhone due to the 3D touch interface that is now the part of the display.