I don't know how useful hours of game footage of college football actually are even though they obviously pour over them. Wouldn't the Heisman guy always be #1 overall if that were the case? They are nearly two different sports. In a workout you can get a better idea of asking a player to do things he'll need to do in the NFL. Of course neither one is really a great evaluation because it's a world of difference with no defense, no crowd, etc. But in the individual workouts you can at least comp a player to a previous one and compare how they looked on a level field. It's a lot harder to do that in game footage with different offense, defenses, supporting players, so I can see why teams put a lot of stock in the workouts. It's a really hard thing to do, thus the fairly low odds of hitting. But I think college game film is basically a resume for most of the players, and the workouts are the interview.