I like pressing to one side (usually the darker side). I think it makes for stronger seams. I also like the way seams nestle together where they meet. Unless the quilt police are in your sewing room, do what makes you happy and what works for you.
By the way, are those the "Happy Cows" from California in your avatar? The commercials on TV are very clever and usually catch my attention when they come on. My favorite one is from a while back when the cows would be laughing because their feet were being tickled by an earthquake (not funny I'm sure if you live there)!!!