I can see more of my surroundings in widescreen on my 30" wide than I could on my 27" 4:3.
Whether the actual dimensions or mathematical figures are different or the same on either, that's not what I was talking about.
For instance, in some FPS like Halo 2, I see more of a weapon in widescreen that is normally not there when on a 4:3 because it's cut off due to the aspect ratio. You can view more to the sides in your vision cone, etc.