Start with your thinking: in the Blocks shown above, BEGIN by matching perfectly the STITCH LINE of the Seams. Don't look at the outer edge, not at this time. When you match and sew the perfect seams, then iron your blocks (open). Do this for both pieces. Then, trim the bigger one down if the seam width bothers you. I would judge if the quarter-inch seam allowance is the problem? or did you cut your 9-patch off-center. Next time, FOLD your 9-Patch block in half, fingerpress the center line as your cutting guide, instead of trying to "measure" it, and then do it for the other center line. Folding in half gives you the perfect center; whereas measuring and dividing by 2 might gum you up. Just my experience here speaking ;0).