Painting a thing (an object stripped of its function or memory) is more interesting. The viewing experience engages more perceptual modes of the viewer; if the brain can't codify/recognize what you are looking at, it's going to keep trying to find a "meaning." This act alone can last for many seconds longer than looking at an image of an object (our brain are very adept at recognizing things). The delay in being able to name the thing might trigger thoughts about the colour, forms, paint, and other material/physical aspects of the painting.
Which is more interesting?