Pressing to the side was because so many quilts were hand stitched and not as sturdy as machine stitching. I agree with the press open on quilts that will get a lot of use. I also agree that it depends on the bulk of the seam being stitched as I mentioned above. I do wall hangings mostly pressed open unless I'm planning on stitching in the ditch, than that is not feasible as the stitch in the ditch has no where to "hang" for lack of a better word.
