The difference between Aurifil and King Tut is that Aurifil is a long staple cotton and King Tut is extra-long staple cotton. The difference is huge and I have found that Aurifil is not a good choice for LA quilting - it breaks all the time because it's not strong enough. I save the Aurifil for piecing and use King Tut for quilting. Love the variegated colors offered by King Tut!!!