I am currently working on both types. I love the freedom of the art quilts, but traditional piecing keeps me focussed. My quilts are not made for exhibitions, though.
Why judges may prefer one over another is a mystery to me. I can overlook technical flaws if the overall quilt has great design and color. Others need every stitch in place, "just so" to consider a piece worthy.
Quilting changes more than any other art I have been involved with - hand piecing purists and longarmers who can enhance a top's appearance with their own artistry. It's all good.