The strength of the "seam" is a reflection of the size & quality of the stitches, not whether they were done by hand or machine. That is the reason why places like Quilts for Kids require everything to be machine quilted. If you look at hand stitched bindings in a guild of 100 quilters, you will see a wide variation in size & quality of the stitches. Some are large & loose, others are tiny and secure. As long as you take your time & aim for something around 3/16" for your stitch length (I prefer a ladder stitch, but I've also used an applique stitch and that also works, just isn't quite as smooth of a finish for my bindings), hand quilting is fine. I have made plenty of baby quilts, quilted changing pads & other items where I finished the binding my hand. They have been washed hundreds of times & there is no indication of any change in the binding -- not so much as a loose stitch.