I get asked all of the time to comment on different cameras. It's not my favorite thing, because vision is most important in photography, not cameras. People spend way too much time worrying about their equipment and not nearly enough time thinking about what they want to create with their equipment. But since I get asked, I write posts like this.
The question that I was asked is, "Which is better, the D7200 or the D5500?" For the answer I'll also throw in the D3300.
All three cameras are capable photographic tools. You won't get better image quality from one than the others. While there are some very minor differences in image quality between them (basically because of how Nikon programs them), the differences are so small you'd never be able to notice, even with side-by-side studies. For practical purposes, image quality is completely identical between the D7200, the D5500 and the D3300.
So what are the differences then, if not image quality? Extras. D3300 is your no-frills camera. The D5500 offers a little more. And the D7200 is fully-loaded. Perhaps the most obvious difference is with the auto-focus systems, which improves with each step up in camera model. But even the D3300's 11-point system is plenty sufficient for most people.
So to answer the question, the D7200 is indeed better than the D5500, which is indeed better than the D3300. But the D7200 isn't necessarily significantly better then the D5500 or the D3300. It all depends on what "extras" the buyer wants. And, if those extras are worth the higher cost.
It's just like buying a car. Do you want the base model that cost less? Do you want the luxury trim with the sunroof, leather seats and premium sound? Or do you want the mid-level that's nicely equipped without breaking the bank?
I can tell you that the D7200 is the best camera of the three, but at the same time the D3300 is the best value of the three. What are you looking for? Do you just want the best? Do you want the most for your money?
If you want tilting screens and WiFi, then the D3300 isn't the camera for you. If you want a weather-sealed camera, the D7200 is the one to get. There are a number of very small differences--it all comes down to which ones you want or don't want and how much you want to spend.
As far as image quality is concerned, it makes no difference which one you purchase, because image quality is the same. So don't worry so much about it.