it's the visual impact first and that usually includes the design, color, and contrast. Sometimes it its the quilting. Since I began quilting I use all types of colors so color itself will not determine my interest.
But it's also what interests me. I am not interested in traditional applique so I won't spend a lot of time looking at a Baltimore album unless the colors, setting, and/or quilting are striking.
Since I got a longarm I pay more attention to quilting details than I used to, also.