Similar story for me. I had the 6 and jumped to the 6s Plus, primarily for the OIS camera feature and better battery. The downside is that it's just a tad big for easy one-handed use. In iMessage, hitting the shift key with the 6s Plus in my right hand is too far to do comfortably. I have to shift the phone slightly in my hand. My next iPhone will probably be the 8 next year and I'll be dropping back to the regular model vs. the Plus.7JB here. Went from 6+ to 7. While i liked the big screen, i would always complain about how i wished i could use it better one-handed. Had the 7 since launch. So far, I'm happy. My wife stuck with the 7+ as she loves the bigger phone.
I believe this is the first time the Plus model is outselling the regular one.