Conceptually and legally it should make no difference. As a practical matter, it would be a story that would hardly make the local news, and would in fact be trumpeted by pro-concealed carry and "stand your ground" advocates as a success story, whether or not Mr. Martin had in fact ever posed a threat to Mr. Zimmerman. Similarly, if Rodney King's arrest had not been videotaped, he would, in the public's perception, be just another asshole in a jail cell, lying about being beaten by the cops.
The major reason this particular story has attracted so much attention, in my opinion, is that it really appears Mr. Martin was a good, photogenic kid who was doing nothing wrong, and his parents seem like nice people. We can all imagine our brother/son ending up in a similar situation, with the same outcome.