Just curious. Are you trolling or do you really think there's a question on this?
Well it is not as clear as it looks if we talking about Jazz bigs - Favors is great help defender but post defense can be better. Big AL is opposite, he is really good one on one defender in the post but absolutely useless as help defender or defending pick and roll. Kanter is kind of mystery to me still, sometimes he shows great individual defense and his pick and roll defense is very adequate as well but most of the time he gets completely lost on rotations and help defense. Millsap is just undersized to be good defender in the paint, he gambles and gets some steals but most of the times opposing bigs score on him easily. We play zone to little to rank them in that regard, but I would say Favors should be the best here as well.
So to sum it up here is how I would rank our defending bigs:
Individual post up defense: Big AL, Kanter, Favors, Millsap
Help defense: Favors, Millsap, tie for Kanter and big AL
Pick and roll defense: Favors, Kanter, Millsap, big AL
Zone defense: Favors, Millsap, big AL and Kanter tie.
So all in all yes, Favors looks like the best defending big on the Jazz.