Yeah I think both phone cameras has their strength. 6s+ daytime photos and video recording is better cause of OIS.I actually like the 6P one more? Am I alone with that? I think the iPhone photos are often "realistic", but a bit boring/bland.
However when it comes to low light the 6p does much better both in pictures and video.
For me personally I have been preferring the 6p because most of my pics are taken n low light situation and the daytime pics are still really good. I don't take much video so the lack of OIS is not a big deal for me. I also prefer a bit over saturation.
However someone who does lots of videos and macro shots and prefer true to life then the 6s+ is definitely the way to go....atleast in regards to camera.