IMO,
crown painted a similar color to the ceiling is super-fantastik, as if it were painted plaster molding. Painted some different color, it's very tricky, because it could look like a stripe; you glimpse it and it draws the eye to it, and fixes your gaze; not good for a harmonious room. It has been done, but only in richly-decorated rooms with lots of other molding/craving detail, and many colors. Hard to pull off well I think.
A lonely strip of dark-stained wooden crown up at the ceiling line, unless the wall colors are equally saturated, is something I really prefer not to see. Very disturbing and stripey to my eye.
Casey