Lori gave you the best answer. I agree that it depends on which look you want. Next to the seam by 1/4 an inch is an "echo" effect, not SID. The ditch is the seam itself. Now, some have reasoned that the stitching slightly beside the actually ditch adds stability to the project, because you catch the seam material that is laid to the side beneath the seam. I have found that when I do that, it ends up distorting the preciseness of my quilt- if I had perfect squares, they can end up looking less than perfect if I SID slightly off-seam. It's a matter of preference- I've always preferred hiding my SID as much as possible- invisible thread and exactly in the ditch. If I was going to go outside the seam, then I would do the echo effect of going an even distance from all seams to create the look I want.