Short answer
Choose diode for accessible non-metal engraving and light cutting, CO₂ for broader and faster non-metal cutting including clear acrylic, and fiber for direct metal marking. No source is universally best.
Diode
Blue-diode systems are compact and efficient for many woods, leather and coated surfaces. Clear acrylic and broad direct-metal processing are not their strength.
CO₂
CO₂ lasers suit clear acrylic and a wide range of organic materials. They require extraction and typically more maintenance, cooling and room than diode platforms.
Fiber
Fiber systems focus energy efficiently into metals for marking and engraving. Desktop galvo designs are fast but often have a smaller field than gantry lasers.
