The disadvantages of physical machining compared with laser cutting (in my experience) are:
1. Fixturing: CNC mills require the material being cut to be clamped -- an extra step; laser cutters do not have this requirement.I like G10, too, and have CNC'd a lot of parts from it. But tooling setup is much more of a pain than with a laser cutter, and throughput -- at least on my mill -- is much lower. Laser cutting, given the right material, is just quicker and easier.
2. Tool diameter: Milling requires cutter compensation, and the sharpness of inside corners is limited by the tool radius. With laser cutting, that's not an issue, and parts can be laid out much closer together for less material waste.