You could do it either way. If you use a .5" ballnose to do the roughing, you won't have all those "stairsteps" to remove; the cutting will be smoother. I doubt that part has enough detail to warrant a 1/16" cutter; a 1/8" tapered ball endmill would work fine. In that case a second roughing pass certainly wouldn't be necessary, and it would go a lot faster. BTW, this looks like a 3D relief, not a 2.5d project, which wouldn't have rounded contours or require a ballnose cutter.