Our quilt guild just had the thread expert educator from Superior Threads as our guild guest speaker. The bottom line is that threads of today are good (exception is the 3 for $1 stuff or too old thread still on wooden spools and reels). Use the thread that your machine and you like. There is no problem using polyester thread on cottons and all cotton or poly/cottons are fine too. Make sure your needle is compatible for your thread and change it often (every project or 10 hours of sewing time). The new titanium needles while more expensive, do last longer. She brought lots of thread and needles for us to play with and it was a great evening.