re: .

Cam was in an spread option gimmick type offense which is not run in the pros, so there was no film of him playing in a pro style offense (in D1 atleast), so you could only speculate as how effective of a passer he would be under center because throwing and making reads out of the option spread is much different than a pro style offense. Also, running the ball was a huge part of cam's game. You could only speculate as to how effective he would be moving the ball downfield if forced to rely primarily on his throwing.

Basically it comes down to known vs unknowns. All of the unknowns previously stated about cam were knowns with Luck (at the college level).
Cam was the #1 pick because of his upside. Scouts know he has all the tools, but it was just a question of whether or not he would be able to transition from Auburn's offense to a pro style NFL offense. We are now seeing that "upside" coming into fruition.