One of the reasons seams have been traditionally pressed to one side is that, in the days of hand piecing, this made the seam stronger (less stress on the piecing thread). That isn't necessary with machine piecing.
Many quilters, especially when making complex patterns, have found it more accurate to press seams open. As long as you are not planning to stitch-in-the-ditch right on top of the seamline, that is fine. Also, you want to be sure not to use a cheap brand of polyester batting that may "beard" through your seamline. I don't use polyester batting, so I'm not sure, but I think the newer bonding processes for this type of batting are pretty good at preventing bearding. It's the spaces between the stitches that creates bigger holes than the fabric for "bearding".