Given that it is an opinion, whoever one chooses to be best is certainly right in their own mind.
Regardless of anyone's opinion, there is very little film out there from the pre-Superbowl era. I consider SI as a valid proof source.
"On this day, Belichick is at first hesitant to break down Brown’s game. There is apparently no real game film of Brown in existence. The Browns have none. NFL Films has none. CBS, which broadcast NFL games during Brown’s career, was unable to provide game film when asked. There are highlight packages available on the Internet and also one fairly complete reel of the 1965 championship game, skillfully cobbled together from various sources. These highlights comprise most of the Brown canon. The rest is lost to time."