When I first started quilting I followed the directions to the "T"---press them to one side, and then as a garment creator first, I realized that I pressed all seams open, and they never came apart---not even in the back of pants---so I started pressing open. The block was flatter, I was able to match seams up better, and now that I am also a longarm quilter, it was so much easier to quilt over pressed flat seams than over those humps. In the end though, I suppose it is what works best for you---for me, I press open.