Pending the model
The model plays an important role here. A wooden ship deck can look enhanced by removing the line and reinforcing any gap with a similarly colored paper; this adds texture and dimension. I like to trace planking anyway to enhance texture, if the scale is large enough.
On some kits, the edges are supposed to be seamless wholes, like the hull of a an advanced spaceship or piece of curved, tempered metal. You have to lose the line for certain or you have something where there should be nothing [a real problem in Congress, but thatís another thread].
I'd rather experiment with shading than leaving the line, when Iím trying to pronounce the difference between two points, even employing wear and weathering techniques. It looks too two dimensional for me to just have a straight line on a model, unless it was supposed to be a painted feature. I try to black lines them as much as possible. This is why I always advocate pre-fitting. It the designer meant the line to be part of the edge, you have to fill a gap with spare or even creative seeming.
Much of it depends on what you wanting to make and how you want it to appear in the end. The more detailed and seamless will take more time and creative shaping.