I must admit, despite my ~$600 dollar investment on my 20'' wide Dell display... I still think the Apple Studio display is quite superior.
The blacks on my Dell is not as dark as the Apple's. There are hints of backlight bleeding on the corners of my screen, which gets annoying when watching dark scenes in movies.
On the flipside, Dell has a much brighter screen and I like its rotation feature. If I get a second one Dell display, I can rotate the 2nd one to a portrait alignment.
All in all I'm happy with the Dell for its price and size ratio. And I also enjoy my newly liberated deskspace.