I like Aurifil for piecing as it is strong but thin. When I first started quilting I used Coats and Clark or Gutterman 50 weight thread for piecing. Most machines are not that fussy about thread for piecing. Find what your machine likes and use that. For quilting, it depends on what your machine likes, the batting you are using and if you are using a walking foot (straight lines) or free motion quilting. Try a good quality machine quilting thread and see what your machine likes. The Superior Thread has a lot of good information on their site about thread.