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

Products
1

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:

SKY%20EYE-U30-01
SKY EYE-U30-01.jpg800×800 154 KB

3-axis gimbal camera:

800x%2003
800x 03.jpg800×800 218 KB

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

2

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