I like to press open. BUT, no matter how many times I backstitch at the end, there's no doubt, the open seam is not as strong. I'm always having unraveling. I back stitch religiously to make sure that won't happen and can never understand why it happens. I use a short stitch to make sure it doesn't happen and can never understand why it happens.
There's just a lot of wear and tear on your pieces while you're working on them and the seam just doesn't hold up.
That's my experience.
But, I'll ditto that they lay flatter, have less bulk and appear much nicer. They just don't hold up as well until you finally assemble everything and quilt it down for good.