I've done both. What I noticed, if I pressed the seams open and used a poly batting, I had a little bearding. If I used W&N or Bamboo batting, no bearding. Never had the issue of bearding come up with seams pressed to one side.
So, what I usually do is if the block has a crap ton of seams meeting (like an intricate PP star) I press open and use W&N. Otherwise, it's whatever I feel like doing.