I love your quilt. Have you considered buying ot making a quilting frame that would allow you to quilt without basting?
I have done almost all of my quilting by machine. Large quilts I take to our senior center so that I can pin baste them on 2-3 tables pushed together.
In answer to your question, however, if it were mine, I would stitch in the ditch on the blocks, but put a pattern, such as a vine, on the sashing.