A lot of it is simply personal preference.
By means of trial and error, so far my favorite thread for piecing is Aurifil 50wt 2-ply. I actually also like this thread a *lot* for machine quilting on my domestic machine. My midarm frame setup thinks this thread is too weak. So far, my favorite thread for the midarm frame is Glide thread (a trilobal polyester).
Many quilters like King Tut thread (all cotton) for quilting. I tried it, but really don't like it for my style of quilting.
I am wondering, though, how big your quilt is. I cannot imagine using 20 spools of thread on a single quilt, and I quilt closely. Maybe you should try out one spool on a sample quilt sandwich to make sure you like it.