I will press open if I'm making a modern pattern that specifies to do so. Note that the little hump you've discovered forms the infamous 'ditch' of 'stitch in the ditch' quilting. If you press open, there is no ditch to stitch in, so that's one thing to keep in mind.
My principal interest in quilting is traditional quilts, and I prefer pressing to the side. I am able to match seams much better when they nest. And truth be told, I enjoy the link to the past that pressing to the side represents. I agree that it comes from the days of hand stitching, when covering the gaps in those seams was necessary.