Let's say i have a SLR with a 1.6x factor. You have a FF sensor, or even a film camera (same difference). I have a 600mm lens, as do you. We are rich, I know. Now, we are shooting wildlife, for National Geographic, while we are at it. The lens/body combo I have will have a longer reach than you will. Yes, it is cropped in camera, no? I have read lots of stories where wildlife photogs sometimes will prefer the crop factor of the xxD series over the 1D series, as it is crop 1.3, thus having more "reach". I think we are talking about the same thing, but you are scientifically saying the same thing i am. A 50D "crop" out the edges of a scene, where as the 5D wont. Just look at the diagram on the right side of the link
yes, but you have to keep in mind that the focal length does not change between formats. a 50mm lens is a 50mm lens on large format, medium format, 35mm, or APS. the only difference is the angle of view.
the reason why cropped sensors are thought of as having more "reach" is because they generally put more pixels in the same area - a 50D has 15MP over its sensor area, but a 5DII only has 8MP over the same area. you also don't have to crop all your images to make the subject larger, since it's already been "cropped" by the camera.