What is the difference between gameobject movement speed by velocity and calculating the speed with deltatime and magnitude ?

This is how i’m getting the camera movement speed in the Update:

cameraSpeed = (cameras[currentCamera].transform.position - lastCameraPosition[currentCamera]).magnitude / Time.deltaTime;

cameraSpeed is float

But when i make:

cameras[0].velocity;

cameras is array type Camera
I see on velocity: Get the world-space speed of the camera (Read Only)

I wonder then why not to use velocity to get and display the camera movement speed ?
And if it’s needed i will add a Rigidbody to the camera then use the velocity i just wonder what is better or what should i use to get and display as the camera movement speed ?

I don’t really understand why you would want to display the speed of the camera, but applying the rigidbody to the camera and displaying the cameras*.velocity.magnitude is about the easiest way you can do it.*