I wish you specified if you are machine quilting or hand quilting. If by machine, it all depends on the look you are going for. sometimes when you outline (assuming you are talking 1/4" to the side of the seam) on both sides, without ditching as well, it makes the area where the seam is poof up. But when hand quilting this effect is not quite as obvious. When hand quilting I usually outlined on both sides of the seam and never ditched. I liked the look of that. But it really boils down to what you want it to look like and if you are fulfilling your batting's minimum quilting requirements.