as a garment seamstress, pressing to the side was awkward, but I was always afraid the batting would work thru the openings of an openly pressed seam (because if I can see the batting, thru the holes, it must be so). The fact that there is less stress on the seam is irrelevant now that we piece by machine and not by hand. Nesting, and Viewing the seam allowance through the fabric, encourages me to press to the dark side. But Bulk wins the day sometimes and I press open. I'm a situational gal.