It's a matter of preference, but I think it depends on the quilt. For instance I recently did 3 the same style. On 2, I just stippled the whole thing. On the 3rd, I did stitch in the ditch around the inner/outer border and FMQ the center and outer border. I liked that look better. If the quilt has appliques, you may want to outline stitch them and FMQ the background to make the applique pop.
The good thing about doing the stitch in the ditch is that if you do it first, you can do the FMQ anywhere you want, you don't need to start in the middle.