There is an argument that the iPhone 6S Plus is essentially a large iPhone 6S. But when it comes to Apple, the conventional wisdom can be misleading. On paper, it does look like an oversized iPhone 6S. It has a bigger screen and a little bit extra in terms of hardware.
basically the iphone 6S plus is just a enlarged mirror copy of iphone 6S which just has a plus added to it in all terms ( monatray, software, hardware, etc)
signing off
R.Tandon