The biggest difference between Book and Rattler is arm talent. Nobody should question that Rattler has a top level NFL arm in terms of velocity and the ability to throw off platform from different arm angles. Book had a peashooter of an arm. It was obvious in college and even more glaring in his time with the Saints. In other words, one player has “potential” tools to be a quality NFL starter and the other had a backup at best caliber arm. Great arm strength isn’t the be all end all on its own, but it certainly disqualify someone that doesn’t have an NFL caliber arm.