I work with a group that ties a lot of quilts for charity type applications, and some of our members are in their upper 80's and older. They have trouble pulling through the worsted weight yarn, and I think it looks "frumpy", so I have them use crochet cotton. It comes in lots of nice colors. Embroidery floss can come in lower grade brands and break too easily, and is more expensive for our application. Crochet cotton we can get at thrift stores.