Todays pros have quads that are way to big. Get real here, these guys today cannot even function let alone hardly walk with their fat legs.
Arnold was the best bodybuilder ever bar none. 
posing was an art back then. its different now, in the age of the freak and whatnot. arnold was an 'aesthetic freak', as in those days, they didnt come much bigger. he kept his lines, muscle shape, density, proportion, conditioning and symmetry, for the most part. the guy got the right advices and used every 1 of them