I only ever used my second card slot for overflow, which means I never used it. Traded my D7100 for a D7500. I never liked the 7100 for a few reasons but love the feel, sound and improved controls of the 7500. The file size is slightly smaller but picture quality is more than made up for with the better processer. The grip feels much nicer in the 7500. The ISO button is in a much better spot. I can take or leave the touch screen, but like the tilt option. The 7500 has made me excited about photography after my disappointment with the D7100.
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The debate about the D7200 versus the D7500 has been raging since the D7500 was first introduced. Let’s recap a few things.

The D7200 was and still is a great camera and until the advent of the D500, it was the best DX camera from Nikon. The D500 introduced a new sensor and a new image processor, as well as a dedicated A/F processor, the same as in the D5 and D850. The D500 is a “professional” camera and as such it does not have a built-in flash as no “professional” would ever stoop so low as to use one. The D500 is also at a much higher price point than the D7200.

The D7500 came after the D500 and its name does underline the bridge between the D500 and the D7200. The D7500 uses the same new sensor and image processor as the D500, but it retains the same A/F mechanism as the D7200 with a few enhancements, such as Group A/F.

The BIG knock many people have against the D7500 is that it only has one card slot. Let’s put that to rest right now; if you absolutely must have 2 slots because your life will come to a screeching halt if the single SD-card fails, don’t even look at the D7500. Just go with the D7200 or bite the bullet and get the D500 and be done with it; end of story and you can skip the remainder of this post.

Now, if you’re like me and you buy brand name cards with high capacity and high performance (Lexar 128GB card,) then the issue of 1 or 2 card slots is irrelevant. Also, I have a great smartphone with me at all times, with gobs of storage space and I can copy my pictures from my D7500 to my Samsung Note 8 in a jiffy using an OTG cable with a regular USB cable attached to the camera, or pull out the SD-card and use a small card reader on my Note 8 to copy the files from the SD card to the storage on the smartphone. These things are very fast and they work quite well. You can also carry multiple SD-cards. Multiple easy ways to do backups in the field. Also, if you lose the camera your dual card slot is of no use to you at that point.

The other thing that the D7500 does not have is a battery grip. If that is critical to you because you don’t have pockets to carry an extra battery, then stop here now. The upside of that is the D7500 has better weatherproofing than the D7200 because it doesn’t have these extra connectors.

The last item that is “missing” from the D7200 is that tab, the link for controlling the aperture on older lenses. If you have Nikon lenses from before 1986, they will not work on the D7500. The upside is the D7500 doesn’t have that tab sticking out of it in the front that is never used or needed for any of the lenses I have or would consider buying in the future.

Did Nikon really cripple the D7500 by reducing the sensor resolution from 24MP to 21MP? If they did, they also crippled the D500 because it has the exact same sensor as the D7500 and with the same image processors, EXSPEED 5. The answer is no, they did not cripple the D7500/D500 with their new sensor. The loss of 3MP is insignificant and the new sensor has reduced noise at higher ISO settings. But beyond that, the new processor is much faster than the one in the D7200 and the buffer is over twice the size of the D7200’s.
This last is important to me. I have been taking a lot of pictures of swimming competitions (daughters) and the higher frame rate and buffer size of the D7500 allows me to take a lot more pictures and get those fun shots that we all want. I’ve also started dabbling with BIF pictures and the high frame rate/large buffer of the D7500 has yielded some great shots.
For those types of activities, and with grandkids and so on, the D7500 is head and shoulders over the D7200. And you get 4K videos.
I’m in my 60s and my eyesight is not what it used to be. I like to chimp my pictures, especially when I’m traveling, to make sure I achieved the shot I wanted (more upfront composition, much less PP). I also like to take pictures of dogs, kids, etc, from their level as opposed to looking down at them. I am also a competitive shooter and I take pictures at such events and so the monitor is important to me. The one on the D7500 is superior to the one on the D7200 in several ways.
First off, it flips up and down, thus allowing me to take picture down low and above my head.
Next, it is much better in bright sunshine compared to the D7200’s. I’ve compared them side by side, and there was no question, no debate as to which is better. I sometimes fit my D7500 to my Kowa spotting scope (20-60X80) to take pictures downrange. This afocal setup requires me to use the monitor and the D7500’s monitor is a joy to use for that. Yeah, I do use the camera a lot outside.
Finally, the D7500 is a touchscreen. That may be a turn off for some, but since I’ve been using smartphones and tablets for a very long time, I’m quite used to touchscreens and it’s nice to have a similar interface for the camera.
In short, while the D7200 is a fine camera and would work just fine for me, I decided on the D7500 because it has the added capabilities that I needed; faster frame rate, much bigger buffer, much better monitor. The things that are “missing” from the D7500 are not things I needed: dual slots, battery grip and the aperture link.

The D500 was the next model up, but it didn’t have a built-on flash. While I own an SB-700 speedlight, I don’t always have it with me, so it’s nice to have that built-in flash. Also, I have no hesitation with using auto mode to take pictures and I even use the scenes, usually sports, for taking a lot of my pictures. I had an SLR (fully manual) in my younger days and I’m well versed in the requirements for exposure; I’m just as happy now to let the camera do it for me for much of my photography. The D500 does not have those things. The D7500 allows me as little or as much control as I want; from full manual to totally automated, P&S-style. No limitations.

My only regret about the D7500 is that I would have liked it to use XQD cards instead of SD, but as I said early on, I have no issues with SD card; I buy brand-name high capacity, high throughput SD cards.

I like the DX format, I like that it extends the range of my lenses and it’s not as heavy as most of the FX cameras. I believe the D7500 is lighter than the D7200; I know it’s lighter than the D500.

Good luck with you choice.