I always try one spool of any brand of thread I haven't used before. Then I know when I find a good sale price of any of them if I want to buy or not. I have a spool of about every brand of thread there is so it doesn't really matter to me. They are all good brands and good thread. Any 50 wt 2 ply or 60wt will give you a thin flat seam. I go by wt. and ply and the right size needle to fit the thread. For bobbin thread I use at least a 70 wt or higher on the biggest cone I can find. Usually Aurifil which is cotton mako thread. I bought a cone of Aurifil black bobbin thread, 80wt 17,000M for $18. It is thin enough the black works great in the bobbin with all med to dark fabrics.