For me it's simple. They are both great coaches who are better in different ways.
Conte gets the best out of his players and makes his teams punch above their weight, but we've yet to see if he can do the same at the highest level.
Allegri is a master tactician who can find the best formula for his teams but obviously, the better his players, the better he can execute his plans.
Conte does better with underdogs, but Allegri is the man to get the potential out of a great team.