I don't know either. I don't care for art quilts very much. They are beautiful and well-crafted, just not for me. I want function, I guess :) I have to say, I've really only made a few quilts so far, and they have NOT been very traditional - one was a wall hanging kit (that one and one other kit I have are the only two kits I will likely do - they are too restricting, but I can learn a lot from them :) ). I made a rail fence that I messed up in a cool way, so it doesn't look traditional. My Trip around the World turned into an X - another mistake that looks really cool (and dh likes it even more :) ) DD's D9P is probably traditional, but it's totally scrappy, so I don't know. The sunflower quilt I'm working on right now is my own design because I wanted to preserve the large sunflowers, so the "squares" are rectangles instead. It does have traditional rail fence blocks incorporated in the design.
I will be making one totally traditional quilt soon - a maple leaf for my oldest son. His request :)