What are the differences between a laser and a CNC machine for relief carving?

Much like some computer numerical controlled (CNC) milling machines, some lasers can effectively carve spectacular details, particularly in wood. There are several differences in the capabilities of a CNC milling machine and a laser, most notable the scale at which each is effective. CNC milling machines are great for large signs and decorative pieces. Relief carving with the laser is more appropriate for smaller items with intricate detail. The time it takes to do a larger piece with the laser would be prohibitive, while the CNC milling machine would have a difficult time handling smaller details. The CNC milling machine may require bit changes in order to achieve finer details.

A major convenience with the laser is that there are no wood chips to clean up – the wood is vaporized, not chipped off. The trade-off is that there is usually some residue from the vaporized wood left behind that needs to be removed. 

   —COOLaserCraft