I've used both 40 wt and 50wt Aurifil threads for quilting. The 40wt is a bit thicker and gives more stitch definition. The 50wt is perfect for piecing and quilting if you don't want the stitches to show as much. It is STRONG!! And my machine loves it because it's lint free. I order my thread from The Quilt Bear since they have free US shipping on every order, no minimum required.

I don't purchase thread at JoAnns anymore at all. Not a good deal on thread there, even with a coupon.