I use Coats & Clark 100% cotton hand quilting thread for the most part, but will buy whatever brand will match the color I'm looking for.
I did try YLI one time and it kept knotting on me. I would look on the backside of the quilt and there would be little knots under there, too. :( Hated that thread. Unfortunately, I had too much done to turn back when I finally got so frustrated with it. :(