Just talked a bit ago today with my best friend who an Apple store manager. Same thing happened this year as last year. The retail channel for the 6s Plus 5.5 inch Pre-orders are dry or will soon be. But there are plenty of 4.7 inch 6s left. I was considering upgrading my 6 but now I'm going for a 6s Plus. all the great features are pretty much lost on the smaller screen version.
This thread: "3D Touch useless on 4.7" Suggested threads below: "3D Touch will be harder to use on the 6s Plus" Both threads: