When piecing I use 2.0 or 2.5 as the stitch setting. As a rule when I am working with small pieces I shorten the stitch lenght. For larger piecies I use the 2.5 . When paper peicing I use 1.0.
Free motion - I set the stitch lenght to 0, since its how fast I move the fabric that determines the actual final stitch lenght.