As I stated, Jabari was completely legit in determining he wanted Duke and it has no impact whatsoever on his fidelity. As I also noted, he's a low key guy and may not want to be in the spotlight that much.
But for a player with a certain mindset...that feels compelled to translate athletic acumen into a vehicle for broadcasting his faith...BYU is a better choice...because it automatically links him to his faith. Ironically, the only guy I think who almost publicly suggested that kind of desire was Jake Heaps. He went big. He wanted the world to know he chose BYU for a reason...and it didn't work out for him.
But Danny Ainge is linked with BYU and as a result is Mormon. Steve Young is the same. They may not have signed up for it...but it's the way it is. So a player who wants that...that is a reason why they might choose BYU. Neither Young nor Ainge served missions...but since leaving BYU there is no doubt they have been prominent ambassadors for the Church...and a good part of that is because they are attached to BYU and BYU is attached to the Church.