Here's a bit of warning from experience with this.
It's a great idea when you're first starting before placing textures. Once you've placed textures, such as when updating an older route, you can end up with broken texture mappings should you decide to update the older 10 meter grid to 5 meter. You may also want to consider this option for up close because the 5 meter grid is 4 times higher resolution, not twice, regarding the polygons needed to generate the ground mesh. Don't get me wrong here; it's great for areas where you need the finer mesh, but consider using 10 meter for the distance where seeing an accurate cut isn't necessary.