Aurifil is a 2-ply thread, rather than a 3-ply, so I assume it is not as strong as 3-ply threads, which is why I haven't used it for piecing or quilting. But being 2-ply, it does take up less space in the seam line. I think the other thing that makes it so popular is all the beautiful colors available. I've used it for applique, and the heavier weights for hand quilting and embroidery. My favorite piecing thread is Masterpiece, which they changed from 2-ply to 3-ply for strength reasons, but that doesn't come in nearly as many colors as Aurifil.