Straight border seams work for me. I only use diagonal seams for making the binding strip to save the "lumps" at the edges of the quilt I'm finishing. If you are afraid your eye will be drawn to a straight border seam, press it open so that it will pretty much disappear when it is quilted. I will admit that I do try not to place any border seams opposite one another. Equally placed border seams seem to draw attention to themselves. If they are staggered, they don't seem to so much. Make sense?