Just don't start using the 6s+ for a few hours after using your 6s. You will start noticing the resolution difference when you go back. The text will start looking rough on the 6s, as the fonts are way smoother on the 6s+... The 1080p does make a difference.
I went back and forth last year between the 6 and 6+ and finally settled on the 6+. It was hard to transition from a 5s to 6+ but the transition from 5s --> 6 --> 6+ was much easier.

You'll start feeling the heavier weight in your pocket but after a week you don't notice it anymore.
Maybe a few months down the road you will decide the bigger 6s+ is the one for you. I definitely am not going for a smaller screen again unless the battery life is as good.