Methinks that carrerascott has the sound upgrade and the blue one does not. I believe that is the location of the subwoofer and possibly extra amplifier. Gently reach into the footwell, towards that hump and you should feel the sub speaker rubber surround and flat cone. Cars without the sound upgrade do not have the sub and larger amp, so no hump.
I do have the sound upgrade though I doubt that explains the lack of shiny parts in the trunk. ;-)