if i am piecing on my janome, any brand of 50wt cotton works just fine.
if i am piecing on either of my brothers, i use YLI 50wt cotton.
i
never use polyester for piecing.
since i have oobledy-googobs of 50wt cotton thread, that's where i start when looking for the right color(s) for quilting.
if i can't find what i need among my cottons, i go through my polyester embroidery threads.
i recently purchased some 30wt rayon embroidery thread.
just a few colors to experiment with when embroidering or quilting.
i will play with it soon for embroidering some stars.
like ... today.
not sure when i'll get around to testing for quilting.