Jules Karney wrote:
...thinking of switching over for basketball mainly....
For sports shooting? ABSOLUTELY NO!
D500 is designed with sports/action in mind... D750 is not. It's a more "general purpose" type of DSLR.
D500 is APS-C, which has a lot of advantages for sports shooters.... you can use smaller, lighter lenses with a crop sensor camera.... especially telephotos can be a lot smaller, lighter and less expensive. Also D500 can shoot at 10 frames per second, has 153-point AF (99 higher performance "cross type", 15 "f/8 capable") that's able to work as low as -4EV light. And it has 1/8000 top shutter speed and 1/250 flash sync, with durability rating of 200,000 shutter cycles. The native ISO range of the 21MP D500 is 100 to 51200 (expandable to 50 and ridiculous 1640000).
D750 is full frame with slower frame rate of 6.5 per second, lower performance 51-point AF (15 "cross type", 11 "f/8 capable") good to -3EV, 1/4000 top shutter speed, 1/200 flash sync, durability rating 150,000 clicks. Native ISO range of 100 to 12800 (expandable to 50 and 51200). As might be expected, a "low resolution full frame" camera such as the 24MP D750 has somewhat better high ISO noise handling than the more crowded 21MP APS-C size sensor of the D500. Full frame dynamic range and color bit depth are slightly greater, too... though the approx. 15 month newer D500 is no slouch in these respects.
Often with basketball and other indoor sports, you'll find yourself shooting under fluorescent or similar types of lighting that cycle on and off very rapidly (120X per second). We don't see it with our eyes, but our cameras do and it makes for a very high percentage of badly under-exposed images. The D500 has Flicker Reduction mode, which senses the light cycle and times the shutter release to the peak output, for far more accurately exposed images. The D500 was the first Nikon to offer this feature for still photos (some video cameras had it previously). The D750 is an older model that doesn't.
Stick with what you've got... for sports there aren't many "better" cameras... it's one of the best.
If you have a specific job where very high ISO are needed, try other methods of noise reduction with what you've got. You might be surprised. I shoot sports with a pair of Canon 7D Mark II and have sold many images shot at ISO 6400, 8000 and even some done at ISO 12800 and 16000. The "trick" with my cameras is to shoot RAW, avoid underexposure at all costs (including using Anti-Flicker when shooting under those types of lighting), then post process with additional noise reduction applied. I use Imagenomic Noiseware, but there are a number of different NR programs which do better with D500 images (ask around... I don't know).
If even that doesn't make for images your customers find satisfactory.... you might need to ADD a full frame camera to your kit. But don't expect it to REPLACE your D500. Maybe if you only need a limited number of images... rent a FF such as the D750 for the job. If renting, a D5 (21MP) or D4s (16MP) would be even better. Those are more sports-oriented full frame models.