Diode lasers have a open working space and is portable, which means it can engrave huge materials with the support of specific software like Lightburn. It is cheaper to some extent. However, for a 50W diode laser, the 50W label includes the power supply. Actually the laser head might be 6W, 10W or 15W at most.
Once you need efficiency in engraving or cut something, the CO2 lasers will fulfill your needs. With the price of a fake 50W diode laser, you can have a Monport 40W CO2 laser which fits its label. CO2 lasers engraving is faster not only because it’s powerful, but also because its track that moves the laser head. A CO2 laser may take more room to place as it needs both an air pump and a water pump wit a bucket.
As for fiber lasers, they are specialized in engraving metals, on which a CO2 laser can engrave. The diode laser can cut metals for about 0.2mm thickness. If you need to customize metal or jewelry for high-end customers, you can consider fiber lasers. And it really works very, very fast even for the 20W ones, even though they are not as powerful as the CO2 lasers.