On caps-a-holic there is a comparison between the Diamond Edition Blu-ray and the Ultimate Collector’s Edition Ultra HD Blu-ray for Snow White and the Seven Dwarfs. I think the colors look more natural on the UHD, and you see more detail than on the Blu-ray. However, I did notice a strange difference in one image:

https://caps-a-holic.com/c.php?a=1&x=533&y=287&d1=18652&d2=18650&s1=220679&s2=220621&l=0&i=3&go=1

If you move your mouse over the image, you can switch between the two versions. On the Blu-ray, you can see thick black lines on the cape, which are probably meant to represent the wrinkles. On the UHD, these lines have disappeared. Personally, the fine wrinkles look more natural on the UHD, but what about the thick lines on the Blu-ray? Which is closer to the original?