As far as Camera upgrade goes, one must take into consideration, their own optical health. No 2 individuals see color exactly the same. I have a fairly good understanding of HiDef Color, Quantification and the differential equations used in mapping color of R.G.B. and C.M.Y.K.
The measuring of color is performed using a Optical Color Density Meter. A very expensive little machine that resembles a top end Fluke V/A Meter. Cost is a around a grand or so.
I'm now retired from over 45 years of technical field service. Started in PPC repair and ended with hi-end large format plotters and color laser printers, both using C.M.Y.K. color. Special emulation thru the embedded controllers allows the C.M.Y.K. to "closely" resemble R.G.B. color (our own eyes see R.G.B.)
In order to facilitate the measurement and quantification of each shade of color in the 16,400,000 colors that comprises the "Pantone" color scheme. Most humans can see Pantone shade differences even without any optical measuring device. The average person sees far less than the 16.4 million colors that is considered the standard for the full color spectrum. 20/20 eye sight and Orbital Ocular Color Dissemination. Very big words to describe just how much color a human eye can detect. The various levels of colors, called "shades" or "steps" generally are not discernible from one shade to the next. Approximately 5 to 10 shades of any color passes before our eyes can actually detect a change in that color spectrum.
The standard grayscale utilizes 256 shades from zero image (white) to 100% image (black). On the average, humans can see about 128, half of 256 shades of gray.
I have a great understanding of imaging, both analog and digital, monotone and full color. Pen plotting, line and imbedded RGB photos to be rendered in a CMYK color. RGB (photo) to CMYK (color reproduction). So how much more BS stuff do I need to write about, concerning colors and steps. This was quite enough! For anyone!
It comes down to this. The 6s+ and the newly released iPhone-7 both have fantastic front and rear CCD's. I don't have a need for more colors or palates. 16.4 million colors are enough for me to use.
Also, consider this little tidbit of information about who is going to be viewing the image and more importantly "what kind of print media or visual display" will be used to view or output (print) that enhanced color image. The ONLY way you can enjoy and view the enhanced colors are with the display from the device that the image was created with.
My 6s+ 128gb device is just fine for me and any rendering of images in partial or full color, will be quite satisfactory on this phones 3D Touch Display. Consider the OUTPUT viewing device or printing device and media used in printing. With 3D printing the colors that are used are more basic than an 8 pack of Crayons.
So again, unless you plan to display your enhanced colors on your new IPhone 7 ONLY, and are not planning on outputting a (3D build) or a color ink reproduction. Then an upgrade to the 7 is just perfect. Otherwise stick with the display of the 6s+.
I guess I'll just have to live with such an inadequate 12mp camera and 3D Touch display of my current iPhone. I'm so disappointed with my iPhone 6s+ because of this inadequacy from Apple. HaHa Just kidding.
I love my iPhone and I'm pretty sure that I have all the bells and whistles I need or think I might possibly need. I may just hold on to this 6s+ and consider it my last iPhone purchase. I'm to damn old to keep trying to remember all the new settings and tricks that come with a new iPhone. Heck, I haven't explored half of the functionality of this device yet.
As in Las Vegas, BlackJack goes, I'm going to hold for now.