I have gone back n forth with both of them. Last 2 years I had the Plus variant but around summer of '16 I got tired of the weight and sheer size of the Plus so I got the 6s. Gotta say I absolutely loved the portability of the 4.7 inch form factor along with all the other positives. But when the 7 came I immediately got the Plus for the better screen, dual camera system, extra 1GB of ram. After a week of using the 7 Plus I went got the smaller one just to compare the both in real day to day use. Loved the smaller form factor again but the fact that it was lacking some features from the Plus I gave it back.
But now that I reflect on having the Plus, the only thing that I really enjoy is the extra battery life. Never used the portrait mode, hardly use the telephoto lens (its not useful in low light) and that extra 1GB of ram seems redundant.
So yeah here I am thinking of getting the 7 again (I have a disease ��

and staying with it for sometime.