Desktop Co2 laser is meant for etching/cutting organic materials like wood, leather and etc. You need fiber laser to etch 3D printed parts, light color PLA can’t be etched as there isn’t enough color pigment to be removed.
For etching plastic, fiber laser is also about 100x faster than Co2. BTW, do not use Co2 laser to cut plastic without industrial grade exhaust system. Otherwise the odds of you getting cancer will be increased dramatically.