The iphone 6s is very similar to last generation iphone 6.infact you wont know it unless you look at the back of the phone.the design of the device very similar to the iphone 6.but one thing to note that is the 6s is slightly heavier than 6 version of it.
For me its a welcome move.bescause iphones were very lighter to use.now to move with the highlighting point of 6s and 6s plus is the 3D touch.and yes I would say its a helpful feature.but the thing is that it does not supports the every app like third party apps.
now if we move to the internals the apple 6s rocks with the new apples A9 chip and 2GB of ram.and that combination is very good.in terms of performance apple 6s is very good.it is very fluidic device.its very responsive device than iphone 6.and also in terms of benchmarks it comes out of the in terms of single core performance.so its a blazingly fast device.
apple has moved the camera from 8MP to 12MP.so its very good thing about the phone.whereas the front facing camera now shoots 5MP pictures.the phone now shoots 4K videos but in terms of pictures if you compare with iphone 6 there is slight improvement.but in the performance of front cameras there is a huge improvement.but in terms of video recording the front facing camera still restricted to 720P recording.
now we have live photo feature.reagarding gaming performance the gaming performance is excellent.the controversy is going with the device regarding chip which is made by TSM and samsung.if you get the device with the TSM chip the device will get more battery life than with the device of samsung made chip.
pros:
fingerprint scanner(touch ID)
camera performance
ram management
optimazation
gaming performance
and best one is SIRI
cons:
it still does not suppoet fast charging
1750 MAH battery
ios restrictions
over pricing