I'm not thinking it is so important for the piecing. It may depend on what kind of thread your machine likes. Some machines are very picky about what tread they work best with. My quilting machine doesn't like the pretty multicolored and expensive threads. I tried to use a multicolored one yesterday, 5 thread breaks in 18" of quilting. Truly it was going to be a long day! Changed to cheapie cotton thread and not one more problem.