I was using Coats & Clark but when I ran out of my navy blue and bought more I bought Mettler which is polyester. Most on this board swear by 100% cotton. I went with the Mettler because with the 1 fabric shop in town -- that's what they sell so it's readily available. If you get 100 different responses, you'll get 100 different opinions. I saw a post a while back that was very helpful to me and that was to look on the website for Superior Threads at their Education tab. There is a TON of information about thread there. I never knew there was sooo much to know about a spool of thread.
http://www.superiorthreads.com/educa...FZZM5QodQ12NLA
Hope this helps :)