I generally sew the binding to the front on the machine and hand sew to the back with blind stitching. I wash my quilts pretty often and have not had an issue with the stitching coming undone. When I do charity quilts, I usually machine stitch to the back and use a decorative machine stitch on the front to sew down the binding for extra durability. I prefer the other way for my own though - I like the look better. Do what you are comfortable with!