I don't think you have to select one method over the other. I think it depends on the block. If you have many layers at an intersection, it may be better to press them open to get it to really lay flat. I generally press to one side, but have read a few different articles/posts that point out good reasons to press open. The link posted above was very interesting. I don't think there's a right or wrong, do whichever you prefer or whatever works for your project! :)