Replying the way the OP did to a person that immiediately judged him negatively as a father for. It automatically going with an iPhone 6 was absolutely appropriate.
To the OP, never tell people you have kids on a forum. They all know how to raise them better than you do.
As far as answering the question, I can't. Your age and the number of kids you have isn't relevant for this type of decision. You can get a good idea of what you're getting with the 7 and 7 plus by just looking at floor models of the 6s and 6s plus. Aside from the camera improvements I don't think you'll have much else to look forward to.