So I'm a college prof and I study stuff like this.  Cognitive ability... everything that happens in your brain... is pretty complex and multidimensional.  One ingredient of it is how quickly your mind can process things.  Imagine two people in a movie with a subtle joke on screen.  One guy gets it instantly and laughs, the other guy has to think about it for a second or two, then gets it, and has a delayed laugh.  I don't know Jeff or Tyler, but it looks to me as an outside observer that Tyler is more like the first guy and Jeff the second.  I do think that speed of cognitive processing is a huge part of success as an elite QB.  The extra second matters a lot when playing against SEC defenses.  The coaches see Jeff all the time at practice, and they say he has great talent.  But under pressure, in the big games, his decisions have consistently been both slow and often very risky.  You never take a risk without a great potential reward, and he didn't get that.  The last thing I want to mention is the eyeball test.  The offense finally started to look a bit better with Tyler.  Maybe he isn't as physically gifted as Jeff, but perhaps the quicker decisions will help.  I am not questioning Jeff's intelligence, that is a broader concept than the ability to think quickly and process many different stimuli instantly.   Take all this with a grain of salt because I have no real idea about each player's ability to make quick decisions, this is based on really limited info.