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Studio Display is finally getting a major update this year, it will have way better contrast thanks to having a miniLED panel.

The current model is nearly identical to your 2015 iMac display
 
I would get an iMac over Studio Display any day of the week. Sleeker, better quality panel, integrated Mac inside, and much better design.

Studio Displays are old, outdated, and an old way of doing things.
 
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