Why would you think image quality would be better in one Nikon vs. another in the same format and vintage with the same sensor and processor? It goes much deeper than that. For what you're shooting, (air shows and beach birds, I'll add sports, racing, children and other fast moving things) the D500 is the better machine by far. The D500 is 2fps faster than the D7500, will take a battery grip, has longer battery life, better bracketing, 3X the screen resolution, 3X more focus points, and a higher build quality to name a few.
What are you giving up with a D500 vs. a D7500? On board flash, scenes and effects modes. On board flash I would very rarely miss. Scenes mode is mostly a white balance specific, (lighting type tool) I don't use, I set my D700's and D750 to auto white balance in most cases unless I want a specific look, then set it accordingly. Most times on my cameras, WB is on Auto, Nikon does a great job with white balance, so why complicate things?. Effects can be interesting to a point, if you're looking for such an ''effect''. I can find the same in most cases in post processing, and more.
It isn't a case of the two cameras presenting the same shot at the same settings, (like writing or reading music) post processing will present the photos, (like preforming the music). Look at the D500 as a high quality instrument with capabilities the seasoned player uses to broaden his music vs. a lower quality instrument with a narrower range. You can play the same music on either, but in this case, the higher quality instrument will give a broader spectrum and be the more useful tool to obtain the raw image to begin with, (you can get a broader range of images and not miss a critical shot with the better instrument). Post processing is your presentation, but if it isn't there to begin with...what do you have? In short, you'll get more shots with the D500 than you will with the D7500. You may not even notice it. If you miss the effects mode, you can gain it back in post processing and make it what you like-how you like.
In my case, I shot film with a pair of Canon F1n's and had a cheap totally mechanical Canon SLR for a back up, just in case. The light meter didn't even work on it, had to use the old Kodak, ''Sunny 16'' rule, but it didn't even need a battery to work and take pictures! I had the basics for 35mm film photography. Then one day, more recently I went digital. Digital scared the hell out of me, I'm not of the digital generation so I decided to start with a camera that wouldn't intimidate me, (so I thought). I looked at Canon, Nikon, and Pentax and Nikon seemed to be what I though I could learn on the easiest, I bought a Nikon D5500. That was a mistake on my part. Yes, it was/is a very easy camera to use if you like AUTO mode, but way too many motions in MANUAL for my liking. With only one command dial I had to remember too many button combinations to get what I wanted. To solve this I bought a D700 which is a 180 degree turn from a D5500 as for manual photography and I felt at home again.
Later I found I would like more dynamic range and a few more mega pixels for low light street type photography. The D750 made the most sense, so I added one to the line up. No-one makes a perfect DSLR to meet our individual needs. We often find two or more model bodies are needed to cover everything we shoot. My opinion is, (for what you shoot) you made the right choices. A D7500 would leave you missing some shots. What you think you miss in the D7500 can be made up in post processing. Affinity Photo is your friend, check it out.
Same photo, first out of camera, nothing done post