What is the difference between 2D vision and 3D vision for robotic arms?

Two-dimensional vision analyzes images in a plane and often suits parts presented at a known height. Three-dimensional vision provides depth or surface information that can help identify object position and orientation when height varies. The appropriate choice depends on how parts are presented and what the robot must measure.
What this means in practice
Three-dimensional sensing can support bin picking or handling objects with varying pose, but it introduces its own calibration, coverage, and data-processing requirements. Transparent, dark, shiny, or overlapping objects can challenge some sensing technologies. More dimensions do not automatically mean better reliability.
Choose the information the task actually needs
A 2D image can be sufficient when objects lie in a controlled plane and their height is known. When object height or orientation varies, the same image coordinates may correspond to different spatial targets. Depth information can help resolve that ambiguity, depending on the sensing method.
Compare the whole pipeline: image acquisition, localization, calibration, grasp selection, and motion planning. A detailed depth map is not automatically a usable pickup target. Test occlusions, reflective surfaces, and difficult poses with the exact parts and presentation method intended for production.
Key points
Use 2D when controlled presentation makes depth unnecessary.
Evaluate 3D when variable height or spatial orientation must be resolved.
Test the exact material, container, lighting, and object arrangement.
Practical example and next step
A flat tray of identical parts may need only 2D localization. Random parts inside a bin may need depth information and collision-aware grasp planning. Compare complete solution performance rather than choosing from camera specifications alone.