In my opinion, the right answer is.. there is no "right answer"! There are times when pressing your seams open IS the best option, for many reasons. It's really a case-by-case decision, depending on the block you're making... or sometimes just the unit within the block you're making. Sometimes you'll do it to avoid bulk, sometimes to avoid having a darker color show up behind a lighter one. If pressing your seams open gives you a smoother and better looking end result, then THAT is the way to go in THAT situation. Your seams shouldn't be any weaker, either. If you fear that they will be, take shorter stitches, and take an extra stitch at the beginning and end of the seam. There's always a way to do what pleases you.
