If I want to stitch in the ditch then the seams are stitched to one side. If free motion quilting, then open seams. I do both domestic machine quilting and LAQ. Bulk at intersections is a consideration. Also, if a particular seam is the edge of a design, to one side adds a little emphasis to the advancing side. If that seam isn't important to the design, it can have less attention if pressed open. Whenever piecing fabrics together to make that piece large enough, ie, piecing borders that are long enough, press seams open. Paper piecing requires the seas are pressed in the direction coresponding to the order of piecing. One of the advantages to Ruth McDowel's paper piecing methods is you can choose which way the seams are pressed.