It depends on the look I want. Finer threads will blend in more and disappear. You can also do closer quilting with a finer thread. Sometimes I want a bolder look and I'll use a heavier weight. I so far I've used Aurifil, Prescencia, King Tut, and Wonderfil for quilting. I have used Star quilting thread in the past but I found it to be linty and slubby. I don't like Coats and Clark or Gutterman.