I came from 5/5s. Its definitely a huge jump for me. The tech stuff (dual camera, screen size and color display, ease of use, memory capacity, volume and clarity, extra features) and size is the biggest factor. The color, its really up to you.
Since you're coming from the 6s, others say most are just upgrades. For me, these are 'holy cow, look what my iPhone can do'.
These thread will help you what others as an iPhone 7/7+ users can suggest. Most members here helped me in my decision making and I'm glad joining this group. What I can suggest is do also your homework in comparing the phone, and try visiting a store so you would see the difference.
I hope my input will help you in choosing your phone.