What's the main difference between 2-axis gimbal and 3-axis gimbal?

Normally there is no zoom and gimbal for FPV camera. For some professional applications, the UAV requires Zoom gimbal camera, the question is what’s the main difference between the 2-axis and 3-axis?

2-axis gimbal camera:

3-axis gimbal camera:

If the price is the same, which one you prefer to?

Yangda Security_Sky Eye-U30_datasheet_waterproof.pdf (571.3 KB)
data sheet of the 2-axis gimbal camera 30x zoom.