It is true that you might as well use up the Mettler-just to use it up. However, it really doesn't matter which thread you use as long as your blocks are consistent. You might need to alter your seam width just a bit. Try a couple and check it out. I have a wide variety of thread brands and use them interchangeably without problem. I do prefer cone thread because of the cost. I piece with white, beige or gray for the most part. Once in a while I use a color just to use it up or empty my bobbins. The goal is consistent size of blocks for easy joining.