Easy way to determine which camera is clicked on?

I have two camera rendering. One fills the view, the other is a smaller rectangle set in one corner of the screen. I can swap these with a script that changes their .rect bounds and swaps their depth. Think of it as a 1st and 3rd person camera picture-in-picture and I can swap them.

Now I want to be able to click on either one, and project a ray to hit things in the scene. Is there a simple clean way of doing this? If I check for Input.mousePosition in bounds of either view, it will always be in the bigger one. I mean I can do this with a bunch of code, but wondering if there was some simple way.

I think it is only 3 lines of code extra.

Camera cam = cameraBig;
if (in rect)
    cam = cameraSmall;

Use cam.