When hand quilting, if you want to stitch-in-the-ditch, you need to press the seams to one side. There is just no real "ditch" if you press the seams open. For hand quilters, I would say it depends on how you want to quilt it whether you press open or to one side. I also find that pressing to one side to form "locking" seams when joining pieces makes my piecing much more accurate. So I still vote for pressing to one side most of the time. I just press carefully to avoid that pleat.