I have a selection of several different weights of Aurifil thread for quilting. 12, 28, 40 and 50. I've used them all for quilting, but only the 50 for piecing.
choosing the weight to use for quilting depends greatly on how much you want the quilting to show. Using a heavier weight (smaller number) will make the quilting very defined, especially if the thread color contrasts with the fabric color.