There are a few subtle differences. For example, on an iPad, you get a matte style with a touch of color, but glossy with barStyle .
Also the border color of the UIBarButtonItem slightly different; with black barStyle they are gray, which simplifies the selection of the dark highlighted state, and with the black color of the hue, the buttons look almost the same in the normal and highlighted state.
I think that a UIBarButtonItem with the "Done" style also looks different, but I'm not sure about that.
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