I press seams for flying geese and HSTs open, and many other seams as well. I don't like the thickness of layers on one side at a corner.

I usually try to press open unless instructed otherwise. I was told a woman in Idaho who does long arm on Quilts of Valor quilts wants the seams pressed open and Nancy Zieman seems to like that way and I just do it without thinking.

I usually press to the side unless it creates a lot of bulk. If it does create a lot of bulk then I press open. Works good for me to do it that way.