For me, whether I press the seam allowances open or to one side depends entirely on the quilt pattern and how the pieces fit together. On the quilt I am piecing now, there is no good or feasible way to press the seams allowances to one side; the bulk on alternate blocks would be huge with lumps everywhere! I have to press the seams open on this quilt.
On the last one I pieced I had to press all the seams to one side ... there are 120 "melons" done in 6-colors, chevron style ... and then I had to top-stitch quilt around each melon because the seam allowances wanted to "escape" and go in different directions where the 6 color strips are sewn together. I'm sure this doesn't make any sense without visual aids, but trust me when I say those melon seam allowances needed to contained because they couldn't be tamed.
I don't think there are any hard and fast rules for any aspect of piecing and quilting. You have to go with what works best for you.