To many this will be a noob question but I'm not shy. I'm just curious about this because I own a Canon Rebel XT and it takes some pretty decent pictures. By decent I mean I could sell. Its a sunny day and there's a bird perched on a park bench. Taking both a Canon rebel and a Canon Mark III out of the box using factory settings I take a shot. If I open the pictures on my PC and look at both what is going to be the first noticeable difference? If you were a camera sales rep what would be the pitch to sell me the Mark III. Obviously mp, shutter speed, lense are factors but lets say the lenses are pretty equal for this question.