#1- Tanner was a freshman, Taysom is a 5th year senior.
#2- Taysom has had arguably the best RB in BYU history playing behind him. Tanner had a LB and a FB running the ball. Tanner did have the luxury of a WR like Mitch Mathews, but overall the WR situation is fairly even, some bad drops have branded the WR's as being worse than they are.
#3- The 2016 defense >>>>>2015 defense. The defense has given Taysom and the offense every opportunity to be undefeated this season. The 2016 defense is one of the best in the country for forcing turnovers. Tanner did not have that luxury.
#4- It is not revising history to point to Tanners 12 games and freshman records, etc. to credit him for being more than lucky. You saying "he made mistakes, but got really really lucky" is bogus. Take away the hail marry vs Neb and your argument crumbles.