I had the "6" last year, and swore I'd never have the 6+ because of the extra heft and size. I wear dress slacks at my workplace 6-days a week, and most guys that carry the larger iPhone look like they have an iPad Mini in their pockets walking around all day...not for me. However, when the 6s/6s+ models dropped, I thought I'd give the Plus model a chance just because I was curious about the added screen size. Within three days of getting the 6s+, and the discomfort of carrying it in my pocket (I knew it...) and the lack of comfortable one-handed use (smallish hands)...and the aggravation of not being able to lock the landscape mode drove me to exchange it for the smaller 6s model.
For me, the 6s is a great size for everyday use. Yeah, I do miss the extra screen size...but it's an easy trade off for me to gain the portability and ease of one-handed use that I need.
But...if Apple can find a way to lose the 1" bezels above and below the screen (a la Samsung) while keeping the screen size of the Plus intact for the "7+" model...I may be one to run back to the larger phone again. Just the lack of device size will help a great deal, and might get me over the hump.