To clarify, the "denser" image is due to a larger chip (not larger pixels) and hence a larger photo area, which will contain more pixels.
So, when you print or view the D750 image on a monitor the field becomes more crowded with more pixels. But, the per pixel field of view is larger.

Of course, the ideal would be to have the D850. with its 4.34 um pixel size (pitch).

Another way to look at it is if, say, you want a head-shot of a bird, with the same field of view, then when you crop to the head, you will lose resolution.

I can upload an example comparison if that will help.

Also interesting is that answer may not be helpful in the final analysis. Let me explain. There is a thing called error of the third type. There are four possible outcomes to answering a question:

1) Is you get the right answer to the right question (a VERY rare event)
2) You get the wrong answer to the right question (a little more frequent and the 1st error type)
3) You get the wrong answer to the wrong question (this 2nd error type is about as frequent as the 1st)
and,
4) You have the right answer to the wrong question (this is the third type of error and is by far the most frequent)

Most people when trying to solve a "problem" do not spend a lot of time thinking about or trying to define their problem. They usually substitute a symptom of the problem or a related issue as the problem itself. They then formulate this issue into a problem statement/question. Here, on UHH, that question is often something like; "which piece of new equipment should I get?" Usually with no more information except possibly a list of choices (two or three at the most.) When I see a question like that, it usually means the person has not thought through the real problem. So I (as do many other truly helpful people on this site) seek clarification on the question. To do otherwise would be unhelpful.

So if someone were to ask me "which type of hammer should I buy?", I am going to ask what job they are trying to do. I am not simply going to tell then "I like my 16oz framing hammer 'cause it feels cool in my hand." I am going to find out if they are building a house or doing metal work. They may need a ball-peen hammer.

I notice on this site how often us photographers get upset when someone disagrees with their comments!
Its as if everyone here is always correct and should not be questioned... NEWS FLASH!!!!! no one here is always right... We share our experiences but sometimes we give opinions about things that we "think" are the correct answers, when they are not. Speaking for me only, having been shooting commercially for over a decade, I see questions on here that I have not experienced but have learned from others the answers that teach me... I am still "teachable". A decade + of experience does not make me an authority on things I have not experienced...
Let us not be anything more than photographers that are connected to the same passions of photography and not PHD's...... Even PHD's need to be taught how to tie their shoes..... LOL

Rather than being the distance between pixels, pixel pitch is the *size* of the pixels. Chip size determines the overall field-of-view. But, resolution is determined by pixel size.
Even though the full-frame Nikon D750 has larger pixels (5.96uM) than the DX format D7500 (4.22uM), when displayed on a monitor or printed, the larger number of pixels provie a "denser" image. If you crop the D750 image to the size of a DX, then it will have lower resolution.

I do mostly astrophotography and so my primary concern is for what's called "image scale", the field-of-view per pixel at a given focal length.

I had a D750 for a couple weeks but returned it for the D7500 because the detail was noticeably less with the D750.

William