I had the benefit of being able to do a home trial of Samsung's higher end 65" 4K HDR displays for my living room. Other than the curved thing, it's my understanding that the KS9000 is pretty much the same as the KS9500. I tried them both for a week, feed them both 1080p, 4k, 4k HDR and noticed no real difference in terms of quality. I didn't care for the curve, but it didn't detract from the image....and I ended up purchasing the non-curved variant.
So for me, there was no benefit of one over the other and I preferred the aesthetics of the flat screen.